Maestro

google

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early 18th century: Italian, ‘master’, from Latin magister .

wiktionary

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Borrowed from Italian maestro, from Latin magister(“master”). Doublet of magister and master.

etymonline

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maestro (n.)

"master of music, great teacher or composer," 1797, from Italian maestro, literally "master," from Latin magistrum, accusative of magister "chief, head, director, teacher," contrastive adjective ("he who is greater") from magis (adv.) "more," from PIE *mag-yos-, comparative of root *meg- "great." Applied in Italian to eminent musical composers. Meaning "conductor, musical director" is short for maestro di cappella (1724), literally "master of the chapel" (compare German kapellmeister).