Green’s Dictionary of Slang

(US) champagne.

1886		E.L. Wheeler N.Y. Nell 5: No more champy at his expense [HDAS].
1892		J.H. Adams Life of D. Hayes Agnew 267: I am free of pains and aches, sleep well, have a good appetite, eat all the good things that come my way, and do not refuse a glass of ‘champy’.
1901		S.F. Call 24 Feb. 10/1: $4 per quart per real old Champy. Dear Champy! what a difference it makes in some people.