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)