Regain

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mid 16th century: from French regagner (see re-, gain).

wiktionary

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From Middle French regaigner (French regagner). Surface etymology is re- +‎ gain.

etymonline

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regain (v.)

1540s, "gain again, recover," as what has escaped or been lost, from French regaigner (Modern French regagner), from re- "again" (see re-) + gaginer, from Old French gaaignier "to earn, gain; trade; capture, win" (see gain (v.)). Meaning "arrive at again, return to" is from 1630s. Related: Regained; regaining.