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!'
An exclamatory remark after being inflicted with pain. Can also be used as a replacement for "oh snap!"
Originates from the human brain not being able to decide which vulgarity to use.
*after being hurt
<person smashes finger>
Person: ohshitdamnfuckow!
Person 2: ...?
*in replacement to "oh snap!" Etc
Mountie: what are you doing in canada?
Leo: what are YOU doing in canada?
Mountie: ohshitdamnfuckow! that hoser owned you!