I trust you completely, Cecil, but I was always under the impression it was from “this for that”. I’m changing my opinion now.
Anyway, that not why I wrote - the main reason I wrote was because the aforemention of “boobs” in your answer brought back to my mind a limerick I used to know a long long time ago:
There was a lady really fat,
Who had 3 sons - Nat, Pat and Tat.
She enjoyed the breeding - The problem was in feeding,
'Cos she realised there was no tit for Tat.
Never bite the hand that… looks dirty!