Green’s Dictionary of Slang

1. (US) an unknown or unspecifiable thing or person.

1918		Lit. Digest 56 77: Student Whoozis is given command of the company. The enemy, either simulated or represented, has his outposts flung across the hills adjacent to and bordering upon the National Highway.
1921		J. Van A. Weaver In American 73: And then him tellin' Pa about some painter That had a exposition in the Institute — All about Whoozis, some new Irish pote.
1926		Wood & Goddard Dict. Amer. Sl. 26: jagamaree. Something for which there is no other name, or whose name is momentarily forgotten; a thingumbob, thingumajig, what-dye-call-it, jiggumbob, jiggalorum, whoozis.
1934		D. Powell Story of a Country Boy 174: You could just him just as nuts about you as Whoozis is about me.
1945		H.C. Jackson ’Round Corners 170: Sometimes, when a friend tells us a story we suspect is pure eye-wash, and when we arch a dubius [sic] eyebrow, and he says: ‘If you don't believe me, ask Joe Whoozis,’ well— We ask Joe Whoozis.
1955		R. Graziano Somebody Up There Likes Me (1956) 229: I don’t care what this whoozis is vice-president of.
1965		L. Bruce How to Talk Dirty 83: You, Mrs. Ralph Whoozis from Alberta, Kansas!
1970		Orbit 52: ‘Gastroenteritis,¹ said Harry, after a pause. ‘Recurrent. Gets worse as you get older, I guess.’ ‘I knew dysentery was recurrent. I never heard that about gastro-whoozis’.
1988		J. Throckmorton Winning Direct Response Advertising 40: Don’t ever put the whoozis before the whazzis.

2. a penis.

1993		L.C. Pike Killer Instinct 77: There he was, in front of God, relatives, and everybody, with his whoozis plugged into his very own vacuum cleaner.
2001		N. Green Shooting Dr. Jack (2002) 184: I’ll give him to you with a bow tied around his whoosis.