Compunction is a noun that means guilt or remorse.
The Latin word pungere (POON Jay ray) means ‘to prick.’ This was combined with C-O-M, a suffix that implies excessive force. That gave us compungere (com poon JAY ray) which meant ‘to prick sharply.’ It may help to think of compunction as a sharp prick or stab at one’s conscience.
Terry was tempted to use the handicapped parking sticker he found in the parking lot, but his conscience wouldn’t let him. As he walked into the store, it occurred to him that compunction has a way of limiting his parking options.