Supporter

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Middle English (originally in the sense ‘tolerate’): from Old French supporter, from Latin supportare, from sub- ‘from below’ + portare ‘carry’.

wiktionary

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From Middle English supporter, supportour, equivalent to support +‎ -er.

etymonline

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supporter (n.)

early 15c., "adherent, partisan," agent noun from support (v.). Meaning "that which supports" is from 1590s.