It's 'oh, shit!' fast, and cut off into 'oh, sh--!' because sometimes someone you can't swear around is in your vicinity. It becomes 'ohsh', following perfectly from the beloved 'oh, shit!'
Oshcore is a term to describe big, fat, plump furries. Like the roundest, nicest furry you can think of. That is HELLA oshcore. If it has GAY furries, that is HELLA oshcore. Big, fat, FUCKING furries.