Green’s Dictionary of Slang

Christmas eve v.

to believe.

1932		‘P.P.’ Rhy. Sl.
a.1945		L. Payne private coll. n.p.: Would you believe it – Would you Christmas Eve it.
1960		J. Franklyn Dict. of Rhy. Sl.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.