A coworker made a sort of cartoon, pompous jerk says "Who dares disturb the ineffable blah blah blah"

Cleaning lady: "Sorry I had no idea you wasn't effable, I'll come back later"

that is to say since effable as a slang term for some someone that one might like to have sex with exists, it is a reasonable pun to make with ineffable as being, well, not effable. However one should probably be able to realize the ineffable in question is not a pun on the slang term and figure things out. Somewhat embarrassing really.

on edit: added in disturb, must have missed it because very tired.

Another meaning the word "effable" acquired in the last couple decades is a spelled out form of "f-able", as in fuckable. OP must've been unaware of the word's prior existence.