Oklahoma is shaped as a short penis with a huge ball sack to go with it.
A Fiddler is one who usually plays flute-like objects. To fiddle, one must place the hand around the flute.
That being said, an Oklahoma Fiddler is one who places the hand around the flute that is shaped like Oklahoma a.k.a handjob giver.
Mark- Yo Steve, how far will Mary go?
Steve- Oh that bitch! I used to dip in that coffee if you know what I mean. She'll go pretty far, a definite Oklahoma Fiddler.