American spelling: to write epistles or letters; to compose or communicate by means of epistles.
From epistle plus the American verb suffix -ize, which converts nouns into verbs. This is the American English variant of the British epistolise.
The -ize ending is actually a Greek borrowing that Americans preferred, while the British kept the -ise from French—and it meant that even obscure words like epistolize became pawns in the spelling wars.
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