The name of the letter H; the eighth letter of the English alphabet.
From Old French 'ache', from Latin 'acca'. The word evolved from the Latin name for the letter, pronounced with an initial vowel sound.
The letter H is famously silent in 'hour,' 'honest,' and 'heir,' which is why saying 'aitch' with an H-sound feels ironic—we literally need a separate word just to pronounce the letter that's so often completely mute.
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