1907: Jackson’s Cloochman
A post-frontier popular magazine with more than the usual number of female writers was among the first to oberve that “cloochman” is a slur.
This 1906 short fiction brings us just about the earliest overt comment I’ve seen on how Chinuk Wawa terms borrowed into English tended to have pejorative overtones.
Her Indian name had been Clalish, but the neighbors called her Jackson’s cloochman, the Indian term for woman, or wife, showing by their very naming of her the white man’s contempt for all of a different race, whatever qualities they might possess.
— from “Jackson’s Cloochman” by Alice Woodruff McCully, in Pearson’s Magazine, page 209, August 1907 (Volume XVI, Number 2)
I’m impressed that an author so long ago explicitly identified “cloochman” (from Jargon łúchmən ‘woman’) as a racial slur.