Archaic third-person singular form of 'do,' used in older English as in 'he doeth' (he does), appearing frequently in the King James Bible and classical literature.
From Old English 'dēþ' or 'dōþ,' the third-person singular form of 'dōn.' The '-eth' suffix was standard for third-person verbs until the 17th century.
Every time you read 'he doeth' in a Shakespeare play or Bible verse, you're hearing grammar that had already started disappearing—by the time the King James Bible was published in 1611, even educated speakers were switching to 'does'.
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