Abarim Publications' online Biblical Hebrew Dictionary
The verb כפף (kapap) means to bend, bend over or be curved, or so dictionaries agree. Here at Abarim Publications we would suggest that our verb additionally means to envelop or contain, with the specific understanding that contents are contained to be extracted (rather than stored indefinitely). Our verb refers to the application of energy (pressure or heat) upon the whole surface of a small and round thing that was designed to contain something, so that whatever exists inside the thing comes out of it. This verb isn't used as such, but in theory it could have been applied to anything from squeezing a lemon in one's hand, to the extraction of iron from a chunk of ore.
Our verb is rare. In the Bible it occurs only five times: Psalm 57:6 speaks of a bowed-down soul, for which enemies have spread a net and dug a pit; obviously reminiscent of an extraction facility. Likewise, both Psalm 145:14 and 146:8 speak of YHWH erecting (זקף, zaqap, a very rare verb meaning to assemble or put together) the bowed-down. Isaiah 58:5 speaks of bowing one's head in generosity, and Micah 6:6 even explicitly asks: "With what shall I come to YHWH, and bow myself before the God on high?"
From this verb כפף (kapap) comes the ubiquitous noun כף (kap), which is one of two main words for the human hand. The other one, the noun יד (yad) refers mostly to one's loving touch (the look-alike verb ידד, yadad, means to love or fondle), or else the power one exerts over something or someone else; hence expressions like to lay one's hands on someone, or to fall in someone's hands. Contrarily, our noun כף (kap) is concerned only with what it contains (or emphatically not; empty or hollow hands are often spread upward in prayer: Exodus 9:29, 1 Kings 8:38).
Our noun כף (kap) occurs about 200 times in the Old Testament, half of which denote the human hand: flat, hollow or open, but always in contexts that emphasize the hand's grabbing, holding, containing or receiving. Our noun frequently occurs in idioms and expressions: clapping hands in applause (2 Kings 11:12) or contempt (Numbers 24:10), shake or slap hands in agreement (Proverbs 6:1), to take one's life in one's hands (Judges 12:3). Violence (חמץ, hamas) contemplated or executed remains in one's hands (Jonah 3:8, 1 Chronicles 12:17, Isaiah 59:6; Psalm 58:2 uses יד, yad).
Our noun כף (kap) often occurs together with רגל (regel), foot, not merely to describe the physical sole of the foot (Genesis 8:9, Deuteronomy 28:35) but rather the range one's "feet" could cover (contain) by walking (Deuteronomy 11:24, Joshua 1:3, 2 Kings 19:24).
Our noun כף (kap) literally means container, and particularly a container used for frequently bringing forth (rather than lengthy storage). It thus may describe the utility vessels that were used in the tabernacle (Exodus 25:29, Numbers 4:7, 1 Kings 7:50), or the hollow pocket of a sling from which a stone comes flying (1 Samuel 25:29). Isaiah 55:12 speaks of trees clapping (or crushing or making very fat) their "hands", which isn't as big a metaphor in Hebrew as it is in English: it speaks of the trees' reproductive organs, their cones and flowers that waft their pollen abroad. Psalm 98:8 likewise speaks of the "hands" of flowing things (verb נהר, nahar, means to flow: what lamps, rivers, stars and happy clapping people do).
Most spectacular is the combination of our noun כף (kap) and the noun ירך (yarek), which describes both the male and female genitalia, and the seat of the "will" (John 1:13, Genesis 3:16; hence also the term "circumcision of the heart"; Deuteronomy 30:6). In Genesis 32:31, the angel of YHWH strikes Jacob on the כף (kap) of his ירך (yarek), which pious translators traditionally euphemize as the socket of his hip joint (which in turn leads to the fantastic dietary stipulation mentioned in Genesis 32:32, which simply does not exist anywhere in Judaism's vast canon). But no, the angel was not concerned with Jacob's hip socket but rather with the functions performed by his genitalia (i.e. his will or desire).
Jacob's youngest son, Benjamin, hadn't been born yet (Genesis 35:16), but until the encounter at the Jabbok, Jacob was a man (and in Hebrew, masculinity describes the tendency to be an individual), whereas after the Jabbok, Israel was a nation (and femininity is the tendency to be a collective; the word אמם, 'amam means both mother and people). The same transition occurs when the masculine Jesus (an individual man) becomes the feminine Body of Christ (a people).
Our noun כף (kap) also serves as the name of the eleventh letter of the Hebrew alphabet, namely the כ (kap), which may also be a prefix that means "as if" and a suffix that indicates the second person single.
The noun כפה (kapa) is the feminine version of the masculine noun כף (kap), and describes a tree's bough from which many fruits hang (Job 15:32, Isaiah 9:14, 19:15).
The verb כפה (kapa) is of unclear pedigree and is thought to mean to subdue or overturn. It occurs only once, in Proverbs 21:14: "A gift in secret subdues anger, and a bribe in the bosom, strong wrath." Here at Abarim Publications we propose that our verb derives from the above and simply means to hold or contain, in the sense of not letting something escape until it's supposed to (like a contained fire, or a contained riot).
The noun כף (kep) means stone; a smoothly curved and moveable stone. It was probably imported from Aramaic (see below). It occurs only in Jeremiah 4:29 and Job 30:6, both times in plural, both times descriptive of places to hide.
The Hebrew language is rather fluidic, with words flowing from roots in predictable and organic ways, and some letters often alternate to form more words and more variations. The letters כ (kap) and ק (qop), however, don't usually alternate. As far as we can tell, there is no root קפף (qapap) in either Hebrew or Aramaic. Still, there are a handful of ק (q) words that look like they derive from קפף (qapap), and have meanings that are suspiciously similar to their כ (k) sound-alikes:
There is no verb נכף (nakap) in either Hebrew or Aramaic, but the verb נקף (naqap I) means to bring in close contact and that usually violently (to knock together, to strike off). The identical verb נקף (naqap II) means to surround or go around. This latter verb could describe a feast celebrating the course of a year (Isaiah 29:1, Job 1:5), a surrounding net to be caught in (Job 19:6), engulfing water (Psalm 88:17), cries heard throughout a large territory (Isaiah 15:8), or making something smooth and round (Leviticus 19:27). Derived noun נקפה (niqpa) describes a rope with which captives are wound and bound (Isaiah 3:24).
From נקף (naqap) derives verb קוף (qop), which likewise means to go around. Noun תקופה (tequpa) describes a coming around, a circuit, a completion of the year (Exodus 34:22, 1 Samuel 1:20, Psalm 19:6).
Noun קוף (qop) is thought to refer to an ape (1 Kings 10:22 and 2 Chronicles 9:21 only). It's probably a loanword of unclear original meaning, but in Hebrew it looks like it means "round one", "round head" or perhaps it described anything caught with a net, or anything that was paraded around. This word is also the name of the 19th letter of the Hebrew alphabet, namely the ק (qop).
The verb כפף (kapap) and noun כף (kap) occur also in Aramaic and with the same general meaning of being curved or hollow, and to contain and bring forth. But Aramaic is much more developed than classical Hebrew, and our verb also occurs in the variation כפיף (kpyp) and the noun as כפא (kp'). The latter is also the Aramaic version of the name of the tenth Greek letter: κ (kappa).
Derived from כפף (kapap), verb כוף (kop) also means to bend or curve, with participles כאיף (k'yp) and כיף (kyp) describing anything bent or curved. The noun כוף (kop), a "round one", describes either a round basket, or a round lid or cover to be placed upon some vessel.
Verbs כפה (kapa), כפא (kapa'), and כפי (kapay) mean to bend over, to invert, to turn upside down. Nouns כף (kep), כיף (keyep), כיפא (keyepa'), כיפה (keyepa) refer to any sort of ball, and specifically to smoothly curved stones or rocks. In the Targums (Aramaic translations of the Bible), this word may describe large boulders in whose shadow one hides (Isaiah 32:2), honey-yielding "curve" i.e. comb (Deuteronomy 32:13, which in Hebrew uses a noun from סלע, sela', to split), or precious gems (Proverbs 3:15). In other writings, our word may describe balls of fire, hail stones, pearls, coral and border stones. Most often, our word describes carefully crafted gems or stones on beaches that were worn smooth by water.
Noun כיפא (keyepa') also means pressure or necessity (something we are bent down by or worn smooth over time). Noun כיפה (keyepa) also means a bending, or an archway or arched doorway, or any kind of bow, like the one produced when urinating. Noun כפותא (kpota') describes a ball of excrement. Verb כפת (kapat) means to twist or tie together. Noun כפות (kapot) means bandage.
Both verbs נקף (naqap) and verb קוף (qop) mean the same in Aramaic as they do in Hebrew. Noun קוף (qop) means ape, and is also spelled קופא (qopa'). Identical noun קופא (qopa') means carrying pole (perhaps a stick that bends from the weight it supports), or archway, or describes a large basket. Likewise, noun קופה (qoppa) means heap or pile, archway, or large basket. From this noun, in turn, comes the noun קפה (quppa), a.k.a. קיפה (qayapa), a.k.a. קיפא (qayapa'), which describes a residue or sediment that remains at the bottom of a cook pot, or coagulated fat floating in water.
In Greek exists the noun κοφινος (kophinos), which describes a large basket, or a comparable unit of bulk volume: a heap of about one basketful. Most experts declare the origins of this word obscure, but here at Abarim Publications we're pretty sure it derives from our Semitic roots כפף (kapap) or קוף (qop). This word occurs 6 times in the New Testament, see full concordance, consistently in reference to the twelve basketfuls of left-over food that were gathered after the miraculous feeding.