Jonesing (Valspeak?) and "mmm hmm" for "you're welcome"

Posted by The Fallen on January 10, 2002

Two quickies... the meaning and origin of the verb "to jones". I suspect valspeak here (and thank you to whoever brought that wonderful term to my attention in an earlier thread).

Also what's the origin of "mmm hmm" being used as a synonym for "you're welcome" in the USA? This still throws me every time I hear it, since in the UK, "mmm hmm" exclusively means "yes" or "I agree".