1
general::
Phrase(s): rinse someone’s mouth out (with soap) [and] wash someone’s mouth out (with soap)
Fig. to punish one by washing one’s mouth out with soap, especially for using foul language. (Usually a jocular threat.) • If you say that again, I’ll rinse your mouth out with soap. • I will wash out your mouth if you swear.
McGrawhill's American Idioms And Phrasal Verbs