A confirmation, made whimsical from swapping word-endings... The usage goes back at least as far as "
Dirty Duck", a comic strip (
graphic novel) written by Bobby London in the 1970's, including the tag line: "Posilutely, Weevil!" "Absotively, Mr. Duck!".
This, in turn, refers back to the theme song by the Gallagher and Shean vaudeville act (big in the 1922 Zigfield Follies), each stanza ending in a punchline, and followed by Shean's query, "
Absolutely, Mister Gallagher?" and Gallagher's reply, "Positively, Mister Shean!"
Blunting the
offense of doubting someone: "You'll be
on time, then? Absotively?", "Oh, posilutely!" (Absotively Posilutely)