Abarim Publications' online Biblical Hebrew Dictionary
The two verbs בלל (bll) and יבל (ybl) both have to do with a flowing or a conveying. Officially they're not related but their forms are certainly adjacent, and they produce similar derivations:
HAW Theological Wordbook of the Old Testament says about the use of the Hebrew verb בלל (balal) in the Bible: "A ritualistic term used of mixing oil into the flour or meal of the cereal offering until every particle of flour was mingled or anointed with oil".
All but one of the occurrences of this verb have to do with mingling or mixing, and that usually of oil with flour (Exodus 29:2, Leviticus 2:4, Numbers 8:8). But the core meaning of this verb is to saturate, that is to fill something until that something can not absorb any more. In Psalm 92:10 the Psalmist cries out, "Thou has exalted my horn like that of the wild ox; I have been saturated with fresh oil".
A curious and quite poetic usage occurs in Hosea 7:8, where Ephraim mixes himself among the peoples. Another off-par usage occurs in the tower of Babel cycle, where God "anoints" (or traditionally: confuses) the languages of the people (Genesis 11:7).
The derivatives of this verb are:
- The masculine noun בליל (belil), meaning fodder (Isaiah 30:24, Job 6:5).
- The verb בלל (balal), which is derived of the preceding noun and means to give fodder (Judges 19:21 only).
- The masculine noun שבלול (shabbelul), meaning snail (Psalm 58:8). A snail makes a slimy trail, which makes it seem as if it is saturated with oil.
- The masculine noun תבל (tebel) occurs in Leviticus 18:23 and 20:12 only, where it describes people having intercourse with animals or in-laws. This word is commonly translated with "perversion" or "confusion" but it seems that the author was less infuriated and indignant than generations of translators, and instead calmly instructs his audience that humans and animals are not compatible in that way: an animal female can not absorb a human male, and vice versa.
- The masculine noun תבלל (teballul) occurs in Leviticus 21:20 only and describes a mass of undissolved material in a person's eye.
The verb יבל (yabal) means to be carried or dragged along by some greater force, and along a course that has a saturated bottom so as not to absorb whatever flows along but rather reject it and push it further. This verb is used for offerings that are being carried along with the worshippers of YHWH (Zephaniah 3:10), or the "feet" or Tyre, that used to carry her to distant places (Isaiah 23:7). Returning exiles are lead home (Jeremiah 23:8, Isaiah 55:12) and Job laments him being carried from womb to tomb (Job 10:19).
This verb's derivatives are:
- The masculine noun יבל (yabal), meaning water course or conduit. This word is used only in plural (Isaiah 30:25 and 44:4).
- The masculine noun יובל (yubal), meaning stream (Jeremiah 17:8 only).
- The masculine noun יבול (yebul), denoting produce from the soil (Deuteronomy 32:22, Habakkuk 3:17).
- The masculine noun בול (bul), meaning produce or outgrowth (Job 40:20 and Isaiah 44:19 only).
- The masculine noun יובל (yobel) or יבל (yobel), literally meaning "a carrier" or "a producer". It may denote a trumpet, i.e. ram's horn (Exodus 19:13, Joshua 6:5), but it may also denote the principle of Jubilee (because no, the year of Jubilee was not the year of the ram's horn, a ram's horn was a producer; Leviticus 25:13, Numbers 36:4).
- The adjective יבל (yabbal), meaning running, in the sense of a running (suppurating) sore (Leviticus 22:22).
- The masculine noun אובל ('ubal), meaning stream or river (Daniel 8:2-6 only; in reference to the river Ulai).
- The feminine noun תבל (tebel), meaning world or land, probably primarily to be understood in the sense of its flows and currents; the economy, whether the natural or the financial one (Isaiah 24:4, Job 37:12, 2 Samuel 22:16). This word tebel is one of two regular words for world; the other is ארץ ('eres). In Isaiah 14:17 תבל (tebel) is used once as a masculine noun.
Scholars identify three separate roots of the form אבל ('bl) in the Bible, and one adverb, which at closer scrutiny are so obviously related that they even very well simply be the same word. The core meaning of all these words is to be swept along in some current or strong flow:
The verb אבל ('abel) means to mourn or lament. It's used in the expectable way of mourning for the deceased (Genesis 37:34, Isaiah 19:8, Amos 8:8) but also in a figurative sense, such as a mourning land (Isaiah 24:4) or a lamenting wall (Lamentations 2:8).
Its derivatives are:
- The masculine noun אבל ('ebel), meaning a mourning (Genesis 50:10, Isaiah 60:20).
- The adjective אבל ('abel), meaning mourning (Esther 6:12, Job 29:25).
The verb אבל ('bl II) isn't used in the Bible so we don't know what it may have meant. Long it was supposed that it was related to similar roots in cognate languages that meant things like to be green or grow green, but (according to HAW Theological Wordbook of the Old Testament) nowadays scholars believe that it is an "Aramaic type of participial form" of the verb יבל (yabal), denoting a being dragged or carried along by a greater force.
The derivatives of יבל (yabal) have to do with water streams or produce that comes forth from the ground. And so it is assumed that our verb אבל ('bl) has that same meaning. The only Biblical occurrence of our verb is in the noun אבל ('abel), which is spelled and pronounced the same as the adjective discussed above. But this noun occurs only as name or name-element. Older interpretations and commentaries will translate this name(-element) with meadow (after the presumed meaning of being green) but younger ones will read stream or brook.
The root אבל ('bl III) is also not used as verb in the Bible, and its sole derivative is again a name: Obil. BDB Theological Dictionary declares that this root is comparable to an Arabic verb that means to be able to manage camels.
The adverb אבל ('abal) affirms. In the Bible's older texts, this sporadically used word appears to have an asseverative force to it; it expresses a solemn affirmation: verily or truly (Genesis 42:21, 2 Samuel 14:5). In later texts of the Bible, however, this adverb appears to express light negations (2 Chronicles 1:4, Ezra 10:13). HAW Theological Wordbook of the Old Testament proposes that our adverb אבל ('abal) is comparable to the adverb בל (bal).
Also note the connection with the root שבל (shabal).