Edith Ordway’s 1914 handbook tells it with the groan built in: “No, not N M E; it’s F O E.”
Spell enemy in three letters.
Give me a hintThe hint
It isn’t N, M, E.
Reveal the answerHide the answer
F-O-E
Source: Victorian conundrum, in How to Solve Conundrums, New York, 1900