Samuel Pepys notes a bit of Court gossip.
Mr. Cooling told us how the King, once speaking of the Duke of York's being mastered by his wife, said to some of the company by, that he would go no more abroad with this Tom Otter, meaning the Duke of York, and his wife. Tom Killigrew being by, said, 'Sir, pray which is the best for a man, to be a Tom Otter to his wife or to his mistress?'. — meaning the King's being so to my Lady Castlemaine.
From Samuel Pepys, Diary (30th July 1667) ed. Lord Braybrooke (1924), iii. 185-6.