1550s, "to snort" (intransitive, of horses), perhaps from North Frisian sneere "to scorn," related to Old English fnæran "snort, gnash one's teeth," and of imitative origin (compare Danish snærre "grin like a dog," Middle Dutch, Middle High German snarren "to rattle").
The meaning "grin or smile contemptuously" is from 1670s; that of "speak derisively, insinuate contempt in words" is by 1707; the sense of "to curl the upper lip in scorn" is attested from 1775. Related: Sneered; sneering. Sneer word is in William Safire's columns from 1980 (he lists so-called, self-proclaimed, would-be, and purported).
"derisive or contemptuous grin," also "verbal expression of contempt," 1707, from sneer (v.).
updated on February 14, 2023