Green’s Dictionary of Slang

exciting; as an intensifier; thus as n. something outstanding.

1884		C.F. Lummis letter 5 Nov. in Byrkit Letters from the Southwest (1989) 73: There, you mush-headed idiots, fix up your darned old world to suit yourselves, if you’re so gee-whizzly smart.
1912		Santa Cruz Eve. News (CA) 6 Sept. 8/3: A Chico officer [...] arrested two physicians for driving their automobiles at a gee-whiz speed.
1920		Lincoln Eve. Jrnl (NE) 1 Apr. 10/5: He was going at a gee-whiz gallop.
1924		Lincoln Star (NE) 29 June 2/6: The assumption [...] that every foreign fighter must be a gee whiz, a near world beater and a sensational performer.
1932		Cincinnati Enquirer (OH) 17 July 64/2: That big bass drum of mine is a gee-whiz.
1936		C. Sandburg People, Yes 31: The bargains brandished with slambang hoots and yells, nods and winks, gee-whiz sales?
1952		W. Winchell On Broadway 18 Aug. [synd. col.] People Today mag’s gee-whiz Boy-Bait on page 39.
1958		E. Dundy Dud Avocado (1960) 66: John was a real, earnest, enthusiastic, gee-whiz tail-wagging prig of an American.
1968		(con. 1950s) J. Healy Death of an Irish Town 56: I [...] listened to the gee-whiz voices of earnest and proud Americans.
1977		E. Torres Q&A 50: ‘I don’t like this guy Reilly, with his gee-whiz bullshit’.
1999		Observer Mag. 1 Aug. 49: A gee-whiz, all American Torque-thrust D racing wheel.
2007		S. Maloney Sucked In 27: Her previous gig as host of a gee-whiz techno-buff show.