What word or phrase does your mother always say?
"private," early 13c., from Old French privé "friendly, intimate; a private place," from Latin privatus "private, personal" (see private (adj.)). Meaning "participating in (a secret)" (usually with to) is attested from late 14c. Related: Privily. Privy Council is from c.1300 in a general sense; specifically of the British government, first attested late 14c., as consaile priue. Privy member "organ of sex" is from late 13c.
"toilet," c.1200, from Old French privé, privee "latrine," literally "private place," from noun use of adjective privé (see privy (adj.)).
An outdoor toilet without plumbing; backhouse, Chic Sale (1662+)