Executor

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Middle English: via Anglo-Norman French from Latin execut- ‘carried out’, from exsequi (see execute).

wiktionary

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From Anglo-Norman executour, from Latin execūtor, agent noun of exequor.

etymonline

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executor (n.)

c. 1300, "person appointed to see that a will is carried into effect," from Anglo-French executour, from Latin executorem/exsecutorem, agent noun from exsequi/exsequi "follow after; carry out, accomplish" (see execution). Fem. form executrix is attested from late 14c. (executrice).

Compare executioner, and also executant "one who does or performs" (especially a musical performer), from 1858; executer "one who performs" (1530s).