Green’s Dictionary of Slang

(orig. US) an indefinite, extremely large number; thus jillionaire, an extremely wealthy person.

1926		Avalanche-Jrnl (Lubbock, TX) 17 Oct. 4: Mr. Allen has a ?ock of scrap books, composed of literally jillions of clippings about his prowess while in profes-sional ball.
1931		‘Reg’lar Fellers’ in Dallas Morn. News (TX) 11 Oct. 5: [cartoon speech bubble]If I had three hunerd million billion trillion jillion dollars I’d give my mom the whole bizniz.
1943		W. Guthrie Bound for Glory (1969) 185: Shucks, they’s ten jillion folks runnin’ aroun’ needs feedin’!
1957		R. Prather Always Leave ’Em Dying 45: Got more money than I know what to do with. Jillion oil wells.
1965		R.L. Pike Mute Witness (1997) 97: I’ll bet I’ve hit about a jillion travel agencies today.
1973		S. Ace Stand On It (1979) 269: Them fucking natives won’t give up and there’s a bout a jillion of them.
1985		K. Vacha Quiet Fire 157: I had to have sex with him a jillion times.
1990		‘Joe Bob Briggs’ Joe Bob’s America 25 May 🌐 Nineteen jillion zillion ‘concerned parent’ groups that think America is being ruined by scary movies and loudmouth rock’n’roll DJs.
1997		C. Hiaasen Lucky You 296: [She] told him to stick with U.S. 1, even though there were a jillion stoplights.