c. 1500, "strange, peculiar, eccentric," from Scottish, perhaps from Low German (Brunswick dialect) queer "oblique, off-center," related to German quer "oblique, perverse, odd," from Old High German twerh "oblique," from PIE root *terkw- "to twist."
Sense of "homosexual" first recorded 1922; the noun in this sense is 1935, from the adjective. Related: Queerly. Queer studies as an academic discipline attested from 1994.
"to spoil, ruin," 1812, from queer (adj.). Related: Queered; queering. Earlier it meant "to puzzle, ridicule, cheat" (1790). To queer the pitch (1846) is in reference to the patter of an itinerant tradesman or showman (see pitch (n.1)).
These wanderers, and those who are still seen occasionally in the back streets of the metropolis, are said to 'go a-pitching ;' the spot they select for their performance is their 'pitch,' and any interruption of their feats, such as an accident, or the interference of a policeman, is said to 'queer the pitch,'—in other words, to spoil it. [Thomas Frost, "Circus Life and Circus Celebrities," London, 1875]