Triumphant

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late Middle English (in the sense ‘victorious’): from Old French, or from Latin triumphant- ‘celebrating a triumph’, from the verb triumphare (see triumph).

wiktionary

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From Old French, from Latin triumphans. Surface analysis is triumph +‎ -ant(“adjective ending”).

etymonline

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triumphant (adj.)

early 15c., from Latin triumphantem (nominative triumphans), present participle of triumphare (see triumph (n.)). Related: Triumphantly.