EXAMPLES FROM THE WEB FOR FESSED UP
"Added the preacher's claim," blurted Terry, and 'fessed up.
And strangely enough when we 'fessed up, he didn't seem astounded in the least.
"I'll tell you about it after Mollie has 'fessed up," evaded Betty, seeming a trifle sorry for her confidence.
At least you have done the square thing and 'fessed up, and now you'll be man enough to take what's coming to you.
shortened form of confess, attested by 1840, American English. Related: Fessed; fesses; fessing.