Less
Old English lǣssa, of Germanic origin; related to Old Frisian lēssa, from an Indo-European root shared by Greek loisthos ‘last’.
wiktionary
Adverb From Middle English les, lesse, leasse, lasse, from Old English lǣs(“less, lest”), from Proto-Germanic *laisiz(“smaller, lesser, fewer, lower”), from Proto-Indo-European *leys-(“to shrink, grow thin, become small, be gentle”). Cognate with Old Frisian lēs(“less”), Old Saxon lēs(“less”).
Determiner and preposition from Middle English lees, lesse, leasse, lasse, from Old English lǣssa(“less”), from Proto-Germanic *laisizan-, from Proto-Germanic *laisiz(“smaller, lesser, fewer, lower”) (see above). Cognate with Old Frisian lessa(“less”).
Verb from Middle English lessen, from the determiner.
Noun from Middle English lesse, from the determiner.
From Middle English lesse, les, from Old English lǣs, as in þȳ lǣs þe.
etymonline
less
Old English læs (adv.) "less, lest;" læssa (adj.) "less, smaller, fewer" (Northumbrian leassa), from Proto-Germanic *laisizan (source also of Old Saxon, Old Frisian les "less;" Middle Dutch lise "soft, gentle," German leise "soft"), from PIE root *leis- (2) "small" (source also of Lithuanian liesas "thin") + comparative suffix.
From the first, the adverb has been used often with negatives (none the less). Much less "still more undesirable" is from 1630s. Formerly also "younger," as a translation of Latin minor, a sense now obsolete except in James the Less. Used as a comparative of little, but not related to it. The noun is Old English læsse.
less (adv.)
early 15c. as a shortening of unless. Extended contraction lessen, less'n, U.S. dialectal, is attested from 1881.
