Be sure to say it in a suitably snooty voice, as this is a strongly classist term. The two pronunciations are the Anglicized and an approximation of the original French form -- for borrowed from French this was, some time in the 1660s or '70s. The French in turn borrowed it from Italian canaglia, pack of dogs, from cane, dog (from Latin canis) + -aglia, a collective suffix that find kinda charming and wish we had in English. Ah, well -- that's what happens when the canaille don't let us have nice words.
He spoke to her with all the haughty contempt of a grandee sneering at the canaille.