What is the origin of the word alphabet?

The word alphabet derives from the first two letters of the Greek alphabet: alpha and beta..

The English word alphabet came into Middle English from the Late Latin word alphabetum, which in turn originated in the Greek ἀλφάβητος (alphabētos), from alpha and beta, the first two letters of the Greek alphabet.[4] 

Alpha and beta in turn came from the first two letters of the Phoenician alphabet, and originally meant ox and house respectively.  Source

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