head: the head on a body, and from that picture the top of a thing, the person in charge, the start of something, the choicest part, and the total of a count.
This is one word whose many uses all radiate from a single picture: the head that sits highest on a body and directs it. The lexicons and the comparative Semitic evidence agree that this is one rich word, not several look-alikes, and that the same network of uses (head, top, chief, beginning, best, sum) was already in place across the ancient Semitic languages long before Hebrew.
From that one picture the senses fan out along two lines. Because the head is the highest part, the word names the top or summit of anything tall, a mountain, a tower, a stairway. Because the head directs the body, it names the one who leads, the chief of a clan, an army, or a nation, and this leadership use is common, especially in laws and lists of officials.
The idea of "first" then branches again. First in time becomes the beginning or opening of a period, the first month, the head of the year. First in rank becomes the choicest or finest, the best spices, the chief joy. And first in counting becomes a sum or grand total, which is why taking a census is literally "lifting the head" of the people.
A few further uses keep the same body-part picture underneath: an army split for a surprise attack moves in "heads," separate companies, and a river that breaks apart has "heads," its branches or sources. Readers should not confuse any of this with a different word spelled the same way that means a bitter or poisonous plant, and so venom or gall; that is a separate word with its own dictionary number.
Nuances
Whether the four "heads" into which Eden's river divides are upstream sources (headwaters) or downstream branches.
- contestedHeadwaters or upstream sources, fitting Eden as the cosmic source of the world's rivers.; Gordon J. Wenham, Genesis 1-15, Word Biblical Commentary 1 (Waco: Word, 1987), 64-66
- contestedDownstream branches: the single river divides as it flows out, on the analogy of a delta.; E. A. Speiser, Genesis, Anchor Bible 1 (Garden City: Doubleday, 1964), 16-17; Nahum M. Sarna, Genesis: The JPS Torah Commentary (Philadelphia: JPS, 1989), 19-20