Federation

wiktionary

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Borrowed from French fédération, from Late Latin foederatio, from Latin foederare; equivalent to federate +‎ -ion.

etymonline

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federation (n.)

1721, "union by agreement," from French fédération, from Late Latin foederationem (nominative foederatio), noun of action from past-participle stem of Latin foederare "league together," from foedus "covenant, league" (from PIE root *bheidh- "to trust, confide, persuade").