1560s, "full of snot," from snot + -y (2). Meaning "impudent, curt, conceited" is from 1870. Related: Snottily; snottiness. Snotnose "upstart" is from 1941; snotty-nose "contemptible fellow" is from c.1600.
Supercilious and disdainful: I won't give that snotty bastard the time of day
[1926+; fr snot and influenced by snooty]