Fibre

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late Middle English (in the sense ‘lobe of the liver’, (plural) ‘entrails’): via French from Latin fibra ‘fibre, filament, entrails’.

wiktionary

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From French fibre, from Old French, from Latin fibra.

etymonline

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fibre (n.)

chiefly British English spelling of fiber (q.v.); for spelling, see -re.