Green’s Dictionary of Slang

(US) an excl. of delight or pleasure.

1943		H.A. Smith Life in a Putty Knife Factory (1948) 90: Then and then only will I yell razz-muh-tazz.
1993		(con. 1930s) M. Verdon Shawlies, Echo Boys, the Marsh and the Lanes 121: My father used to say, ‘Raz as me daz ah, I’m going down Pa’na’. That means it was lovely.