Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 13c., "an order from an authority," from Old French comandement "order, command," from Latin *commandamentum, from *commandare (see command (v.)). Pronounced as four syllables until 17c.
Of þe x commandements ... þe first comondement is þis, O God we ssul honuri [c.1280]