how's your father

Meaning

Noun

• A whatsit; a thing which the speaker is unable or unwilling to specify more precisely.
• Sexual intercourse.

Origin

• how + is + your + father. A popular catchphrase of the 1910s popularised by music-hall entertainer Harry Tate, who used it for comic effect to change the subject away from one about which his character was ignorant (hence sense 1) or a taboo subject (hence sense 2).