Fortitude

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Middle English: via French from Latin fortitudo, from fortis ‘strong’.

wiktionary

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From Middle English fortitude, from Old French, from Latin fortitūdō(“bravery, strength”), from fortis(“brave, strong”).

etymonline

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fortitude (n.)

late 14c., "moral strength (as a cardinal virtue); courage," from Latin fortitudo "strength, force, firmness, manliness," from fortis "strong, brave" (see fort). From early 15c. as "physical strength."