From an unused root meaning to be sharp. Shēn refers to a tooth in both literal and figurative senses, as well as ivory (elephant tusk) and rocky crags (sharp cliff faces, as in 1 Sam. 14:4). The word plays on the idea of sharpness — teeth that bite, ivory that is precious, cliffs that are dangerous.
The range of meaning in shēn opens multiple theological windows. Lex talionis — the law of 'tooth for tooth' (shēn tachat shēn, Ex. 21:24) — is not a mandate for revenge but a principle of proportional justice: punishment must fit the crime, no more and no less. Jesus addresses this in Matthew 5:38-39, not abolishing the principle of justice but calling His disciples to a higher ethic of non-retaliation. Ivory (shēn) appears in the prophetic condemnations of luxury and excess — Amos 3:15 pronounces doom on 'houses adorned with ivory,' signaling wealth acquired through injustice. Whiteness like teeth appears in Genesis 49:12 in Jacob's blessing of Judah: 'His teeth whiter than milk' — a picture of abundance and kingly vitality. From justice, to wealth warnings, to blessing — the word carries surprising range.