Green’s Dictionary of Slang

(US) elegant, smart; if used of people, with an undertone of self-satisfaction and/or condecension.

1931		L.A. Times 13 Dec. III 1/5: And you should have seen all those snitzy Liberal Arts students when they found out. It was just too killing.
1943		J.A.W. Bennett ‘Eng. as it is Spoken in N.Z.’ in AS XVIII:2 Apr. 89: There is a liking for words in -er, and a whole group of them express admiration: [...] snitcher (cf. U.S. snitzy) [...].
1954		Tampa Bay Times (St Petersburg, FL) 7 May 25/3: Oh boy — are bobby-sex getting snitzy! The latest have ruffles round their cuffs.
1965		Ogden Standard Examiner (UT) 24 Aug. 13/1: You know how people are treated by maitre d’hotels, headwaiters [...] in snitzy stores.
1974		Times (San Mateo, CA) 22 July 14/1: Folk music was in the repertoire for sophisticated clubs [...] ‘the snitzy joints’.
1985		St Louis Post-Dispatch (MO) 26 May 382/4: Snitzy: a combinationof snippy and ritzy. ‘She’s certainly gotten snitzy since she moved to Ladue’.