Green’s Dictionary of Slang

sypho n.

[abbr. SE syphilis + -o sfx (3)]

1. (Aus.) syphilis.

[Aus]‘Beaufort’ in Mess Songs & Rhymes of the RAAF 29: He must have been riddled with sypho or gonna.
[Aus](con. 1941) E. Lambert Twenty Thousand Thieves 99: The joker who owns this has sypho. D’yer mind?

2. (US gay) a syphilitic.

[US]B. Rodgers Queens’ Vernacular 206: syph-o a syphilitic.