slight: [13] The ancestral sense of slight is ‘level, even’. It goes back to a prehistoric Germanic *slekhtaz, a word of unknown origin which had that meaning, but whose descendants have diversified semantically beyond all recognition (German schlecht and Dutch slecht, for instance, now mean ‘bad’, having arrived there by way of ‘level, smooth’ and ‘simple, ordinary’). ‘Smooth’ was the original meaning of English slight (Miles Coverdale, in his 1535 translation of the Bible, recorded how David ‘chose five slight stones out of the river’ to confront Goliath with (1 Samuel 17:40), where the Authorized Version of 1611 has ‘smooth stones’), and it survived dialectally into the 20th century.
By the 14th century, however, it was evolving into ‘slim’, and this eventually became, in the early 16th century, ‘small in amount’. English acquired the adjective from Old Norse sléttr ‘smooth’, and Old Norse was also the original source of a verb slight [13], meaning ‘make level or smooth’. This died out in the 17th century, however, and the modern verb slight ‘disdain, snub’, first recorded at the end of the 16th century, is derived from the adjective, in the sense ‘of little importance’.
The noun comes from the verb.
slight (adj.)
early 14c., "flat, smooth; hairless," probably from a Scandinavian source akin to Old Norse slettr "smooth, sleek," from Proto-Germanic *slikhtaz (cognates: Old Saxon slicht; Low German slicht "smooth, plain common;" Old English -sliht "level," attested in eorðslihtes "level with the ground;" Old Frisian sliucht "smooth, slight," Middle Dutch sleht "even, plain," Old High German sleht, Gothic slaihts "smooth"), probably from a collateral form of PIE *sleig- "to smooth, glide, be muddy," from root *(s)lei- "slimy" (see slime (n.)).
Sense evolution probably is from "smooth" (c. 1300), to "slim, slender; of light texture," hence "not good or strong; insubstantial, trifling, inferior, insignificant" (early 14c.). Meaning "small in amount" is from 1520s. Sense of German cognate schlecht developed from "smooth, plain, simple" to "bad, mean, base," and as it did it was replaced in the original senses by schlicht, a back-formation from schlichten "to smooth, to plane," a derivative of schlecht in the old sense [Klein].
slight (v.)
c. 1300, "make plain or smooth," from slight (adj.) Meaning "treat with indifference" (1590s) is from the adjective in sense of "having little worth." Related: Slighted; slighting.
slight (n.)
1550s, "small amount or weight," from slight (v.). Meaning "act of intentional neglect or ignoring out of displeasure or contempt" is from 1701, probably via 17c. phrase make a slight of (1610s).
