Green’s Dictionary of Slang

surreptitious.

1970		H. Oster ‘Background of the Blues’ in Szwed Black America 143: I was the on'iest jack of the family. [...] So my life was just that way, to keep out of trouble, drink my little whiskey, an’ go an’ do little ugly things like that, but just in a cue-tee (quiet) way.
1979		‘Iceberg Slim’ Airtight Willie and Me 123: Pad rent for her junkie brother and her Q.T. sweetie.
1989		J. Morton Lowspeak.
1996		L. Pettiway Honey, Honey, Miss Thang 215: In Falk Corrections Center. And I had a husband know [sic] as Q.T. Gorgeous daddy.