In Wales road signs are printed in both English and Welsh. When a new sign was being made someone sent the English part to a translator, who’s out of office message was in Welsh. They assumed that message was the translation and printed it on the sign.

https://www.snopes.com/fact-check/mistranslated-welsh-traffic-sign/

Not a translation error but the worst tattoo I ever saw on someone was a guy with a bloody tampon tramp stamp.