Origin of smoltLate Middle English (Scot): probably akin to smelt
intransitive verbsmolt·ed, smolt·ing, smolts
Origin of smoltMiddle English from Medieval Latin smoltus probably of Old English origin
(comparative more smolt, superlative most smolt)
From Middle English smolt, smylt, from Old English smolt, smeolt (“mild, peaceful, serene, still, gentle, clear, bright"), from Proto-Indo-European *smultaz, *smeltaz (“quiet, gentle"), from Proto-Indo-European *(s)meld- (“to beat, grind, crush, make weak"). Cognate with Scots smolt (“calm"), Old Saxon smultro (“quiet"), Middle Dutch smolt, smout (“weak, gentle, quiet"), Middle High German smolz (“dear, lovely, beautiful, sheen").
Probably an alteration of smelt, due to smolt (“smooth"). See above.