Abarim Publications' online Biblical Hebrew Dictionary
The feminine (and rarely masculine) noun ארץ ('eres), meaning earth, occurs all over the Semitic language spectrum and is probably related to the Indo-European root that also produced the Germanic nouns earth, erde (German) and aarde (Dutch), and possibly also the Greco-Latin root from which comes the word terra. Where this obviously archaic root comes from, which primal idea is expresses, is utterly unclear, but its modern usage is certainly not on a par with the original one.
In our modern space age, in which we get our grub mostly from the supermarket, we think of earth as a planet sitting in space much more than arable land and its many functions and comforts, but our word and its most defining applications come from a time when the opposite was true. Our word may even be as old as to express something that was fundamental in the pre-agrarian period, namely both traversable land in contrast to water, and land in contrast to the sky (which in turn suggests that terms were not necessarily invented solely as duos as Zoroastrianism likes to propone, but may in fact reflect multiple axes of symmetry).
It seems logical to assume that land as the traversable part of existence was understood to be limited by water horizontally and sky vertically, while the ancients doubtlessly also observed that peninsulas and islands allowed for excursions into the realm of water and mountains allowed for excursions into sky.
Cognition and the hydrological cycle
We enlightened moderns have no problem with the metaphor that equates knowledge with light (which are really two entirely different things and not in any way related in a strictly physical way) but to the ancients, rain held a similar and equally valid meaning, namely that of the conveyance of instructions, or the joint act of someone teaching and someone else learning from an instructor (see our article on the word Torah). In other words: the word for earth essentially expressed the present state of affairs, the now, while understanding that to the ancients the present was not a featureless blip on a digital watch, but rather the indefinite stretch of observable reality which took eons to build.
Water is neither past nor future but both; it's unapplied raw material that waits to be incorporated in the earth. That's why it is released over the surface of the earth in the form of rain: to make to earth grow. And this also indicates that not all mentions of drought in the Bible are bad. When the earth has reached its fullest potential, it will wed the heavens (Revelation 19:7) and there will be no more raw material to build the earth up further. Hence there is no more sea (Revelation 21:1).
Terrestrial water in all its forms (seas, rivers, ground water) was seen as akin to knowledge in all its guises (culture, schools of thought, intuition), whereas rain became connected to instruction and formal teaching. That made the sky or heavens (שמים, shemayim) the storeroom of all (future) knowledge as well as the final destination of any traveler, and from there it's no big leap to begin to recognize the celestial bodies as teachers, guides and deities, and the sky as the heavenly abode of both gods and deceased people (Genesis 1:14, Deuteronomy 4:19, 1 Kings 22:19).
Note that this idea is no longer shared in the modern world. We like to think that there's an undiscovered territory out there, with knowledge to be obtained that has never been known to anyone, but the ancients where very much aware of the hydrologic cycle (all rain comes from the sea and has already once fallen; see Ecclesiastes 1:7 and 11:3; also see Isaiah 55:10-11) and thought rather in terms of floods versus dry spells, also where the cycles of knowledge were concerned.
The Hebrew model was obviously much more sophisticated than that, and even though tradition has diligently tried to murder Genesis 1, its traditional interpretations have been largely discarded but the model itself is uncontested (see for more details our introduction to Scripture Theory). In the Hebrew model, reality is depicted as one member of a two-some that exists within an entity known as "the beginning" and the "Word of God" (Genesis 1:1, see Colossians 1:15-17, John 1:1-3) and that two-some is existence versus non-existence. Existence in turn is comprised of two elements, namely potential versus that which moves between zero and potential (heaven versus earth). Earth started out as water but the water focalized (see our article on the word לב, leb, meaning heart) and formed dry earth. Then the dry earth brought forth vegetation, and provided a fundament for other creatures, and all this obviously goes much further than a primitive creation myth. Genesis 1 reflects the most fundamental process via which complexity progresses and can be applied to any facet of existence.
In the sequential Scriptures, the word ארץ ('eres) is commonly translated mostly with the word land, but it should be remembered that in antiquity a land was not defined as an area marked by borders and such, but rather as an area in which a specific culture existed that was based on a specific body of knowledge (in the broadest sense, from literature to agriculture to rules of engagement of other cultures). Hence our word may denote the whole (known) world (Genesis 18:18, Jeremiah 25:26, Isaiah 37:16), or the whole library of knowledge enjoyed by the peoples of the world (1 Samuel 2:8, Psalm 75:3, see Proverbs 9:1). It may denote a country or territory, again not as geographic area but as cultural area (Genesis 10:10, Joshua 11:3, 1 Samuel 9:4) or soil which may be cultivated and made to produce (Exodus 4:3, Leviticus 19:9, Ruth 2:10).
Likewise, the land of death, of which Job speaks so pungently, should not be understood as a physical place somewhere but rather a place where no knowledge can be enjoyed or traded and nothing grows (Job 10:21, see Isaiah 38:18).
Another word that is often translated with land or earth is תבל (tebel).