Gee... you're sooo "so"!

Apparently the word "so" used to have by itself the meaning of gay, homosexual. The OED cites one of its early usages in this sense:

b. slang. Homosexual. Obs.

1937 in PARTRIDGE Dict. Slang. 1963 C. MACKENZIE Life & Times II. 254 ‘I've come to the conclusion,’ he told me, ‘that I'm not really “so” at all. I much prefer girls.’ At this date [sc. 1899] the cant word among homosexuals for their proclivities was ‘so’. That seems to have vanished completely from current cant. 1968 J. R. ACKERLEY My Father & Myself xvi. 192 A young ‘so’ man, picked up by Arthur in a Hyde Park urinal. 1973 Daily Tel. (Colour Suppl.) 23 Feb. 51/4 Wilde used to call him ‘the architect of the moon’. Rothenstein, Beerbohm,.. and Epstein were his more predictable friends, as he was not.. at all ‘gay’, as it is now called, or, as it was then called, ‘so’.

Language Hat readers entertain a discussion on the etymology of this use. The most inspiring hypotheses are a dutch derivation from the word "zo" and the more straightforward so = "that way", which contextually nudges to the salient meaning.