残す
のこす · nokosu · JLPT N3 · verb-godan
to leave
🍱 残 = remain + す = make it remain: leave it behind, save it for later
残す is the transitive partner of 残る (nokoru, to be left over): with -su you leave something, with -ru it stays. The same 残 appears in 残念 (zannen, regret), which means a thought that stays with you. Sound hook: nokosu, there's no cost to leaving some for later.
残 — 歹 (bones/death) + 戔 (small/cut, phonetic)
A semantic-phonetic compound: 歹 (bare bones, death) gives the meaning of harm or ruin, while 戔 (two 戈 spears, suggesting cutting) supplies the sound. Originally meant to injure or destroy, later extended to 'remnant, leftover' — what remains after damage.