I know It When I See It (http://archiveofourown.org/chapters/841453) Hot and also very funny. Its Sam/Cas.
Summary: Cas helps Sam translate a Medieval Enochian text that turns out to be racier than expected. Awkwardness ensues.

This is actually linked to a COMPLETELY different fic, but I (complete stranger that I am) am so not complaining cuz it's a brilliant story that I never would have read otherwise. In fact, THANK YOU.

Oh crap! Sorry, I had just recced that for another request and I must've still had it on the clipboard. It was a really good story though wasn't it? :)

This is the link I was trying to give you http://archiveofourown.org/works/737320 by balder12

Thanks for both links! ;-)