Scruple (noun)

1. A feeling of doubt or hesitation with regard to the morality or propriety of a course of action.
2. A moral principle or position.

Origin:

From middle english scrupel, from old french escreuple, from latin scrupulus ("a small sharp stone, a thorn, a scruple"), diminutive of scrupus ("sharp stone, rough or rugged object"), from proto-indo-european *sker- ("to cut").

Examples:

1. He had no scruples about lying to his boss.
2. She had a scruple about taking advantage of her friend's trust.
3. He had scruples about accepting the gift because it seemed like a bribe.
4. She had scruples about breaking the law, even if it was just a small infraction.
5. He had a scruple about accepting the promotion because he felt he hadn't earned it yet.