I recently ran across a quote attributed to Oscar Wilde. Someone made the accusation the vocabulary was not used during his time and this could not possibly be his quote. The quote in question:
"Everything in the world is about sex except sex. Sex is about power."
The first attested use given by the OED is from H.G. Wells' Love & Mr. Lewisham in 1900:
We marry in fear and trembling, sex for a home is the woman's traffic, and the man comes to his heart's desire when his heart's desire is dead.
And it took a few more decades for the usage to really take off, at least in writing.
So although "sex" in the sense of "sexual intercourse" was probably just beginning to come into use by the end of Wilde's life (he died in 1900), it seems very likely that this quote is misattributed; I can't find any source for it. And he's definitely one of those historical figures that people love attributing quotes to, as Dorothy Parker pointed out (in the June 2, 1927 issue of Life):
If with the literate I am
Impelled to try an epigram,
I never seek to take the credit;
We all assume that Oscar said it.
This 2002 book seems to attribute the quote to a psychoanalyst by the name of Robert Michels, and it is one of the earliest references that I could find, but of course it's possible that he was quoting someone else.