yet another random thought..

Why in the hell do they call a $5 bill a 'fin' ? Who started this tradition and more importantly, why ?

I remember the first time I heard the term. (memory cloud appears)....I was about 5 or so and my father asked me if wanted a fin for spending at the movies with my other cousins. I was like "say what?...ohh...a fin?" Deep in contemplation at this point....I said "huh? why would I want a fin?". All I could do was picture myself with fish-like fins in place of my arms and legs. All my family could do is laugh.

Even to this day, even though I am QUITE familiar with this term, I still do not understand this concept. Does anyone out there know ?