hydronym
n. the name of a river, lake, sea, or any other body of water

A bizarre exchange from E.S. Turner’s 2012 What the Butler Saw, a social history of servants in English society:

Vain young gentlemen had a way of summoning their valets to answer questions to which they well knew the answer. [Beau] Brummell, when asked by a bore which of the Lakes he liked best, rang for Robinson. ‘Which of the lakes do I admire most, Robinson?’ he asked; and was informed, ‘Windermere, sir.’ ‘Ah, yes, Windermere, so it is. Thank you, Robinson.’