For a long time I’ve thought that the currnent fashion for using “gender” to refer to people as opposed to grammar was a recent fad associated with political correctness. But it seems I was wrong. I’ve just come across this in Tristram Shandy (Ch2.XXVIII).
To those who do not yet know of what gender Bruscambille is – inasmuchas a prologue on long noses noses might easily be done by either…
So that puts the usage back at least to 1759.