Farb

Or "Farby". Historical Reenactor slang, shortened for Far-Be-It-From-The-Truth. Meaning an element of someone's historical representation is not correct and true to history.

Can also represent "FUBAR", F*cked up beyond all repair.

Synonyms- inaccurate, incorrect, or illegitimate.

"Yeah, Jon's WWII uniform is FARB, he uses equipment that came out 60 years later."