A one-hundred dollor bill. C stands for "centum" the Latin word for 100. The word "note" actually come from the bill it's self. Which reads, "This note is leagal tender for all debts, public and private."
customer: how much does this skirt cost?
cashier: a c note
customer: huh?
cashier: one hundred dollars you moron you're gonna buy it or what?
customer: no you can keep it b!tch! a c note you gotta be out your d@mn mind!
The musical note achieved when a stripper flicks the stud on her pierced hood as if it were a tuning fork. If done correctly this technique can emulate the full octave range of C on the scientific pitch notation table.
guy1: So how was the strip club
guy2: what?
guy1: The strip club...how was it
guy2: What stripe? I can't hear you guy1: Ah... she hit a C note didn't she