also diss, slang, by 1980, shortening of disrespect or dismiss, originally in African-American vernacular, popularized by hip hop. Related: Dissed; dissing. Earlier it was short for distribute in late 19c. printers' slang and for disconnected in the telephone-line sense, and in this sense it was given a slang figurative extension as "weak in the head" (1925).
1520s, "omit to do or perform;" 1530s, "treat carelessly or heedlessly, treat with disrespect or without proper attention or care;" from Latin neglectus, past participle of neglegere "to make light of, disregard, be indifferent to, not heed, not trouble oneself about," literally "not to pick up," variant of neclegere, from Old Latin nec "not" (from PIE root *ne- "not") + legere "pick up, select," from PIE root *leg- (1) "to collect, gather." Related: Neglected; neglecting.
1560s, "triumph over in an arrogant way" (obsolete), from French insulter "to wrong; reproach; triumph arrogantly over," earlier "to leap upon" (14c.) and directly from Latin insultare "to assail, to make a sudden leap upon," which was used by the time of Cicero in sense of "to insult, scoff at, revile," frequentative of insilire "leap at or upon," from in- "on, at" (from PIE root *en "in") + salire "to leap" (see salient (adj.)).
Sense of "verbally abuse, affront, assail with disrespect, offer an indignity to" is from 1610s. Related: Insulted; insulting.