unmentionables

adjective

1. not mentionable; inappropriate, unfit, or improper for mention, as in polite conversation; unspeakable.

noun

2. something that is not to be mentioned: That subject was classed among the unmentionables.
3. unmentionables,
   1. undergarments.
   2. (formerly) trousers or breeches.

pl n

1. mainly jocular underwear

adjective

1. 1. unsuitable or forbidden as a topic of conversation
   2. (as noun)the unmentionable

adj.1837, from un- (1) “not” + mentionable. Unmentionables “trousers” is attested from 1823; meaning “underwear” is recorded from 1910.