Possible Clues:

• It hurt to take small coin out of sporran
• Hit sign?
• Comment upon receiving a large bill
• Exclamation when penny falls from pocket
• Response to many a punch line
• Lift head off sofa with cry of pain
• Cry of pain when losing a bit of composure in bed
• Klutz's outcry
• Hard-hitting response?
• Opposite of "aah"