'fibre' (from which 'fibred' derives) originates from Latin, specifically the word 'fibra', and ultimately from Greek 'phíbra' meaning 'fiber' or 'filament'.

'fibre' came into English via Old French 'fibre' from Latin 'fibra'; the English form 'fibre' (and its derivatives like 'fibred') developed through Middle English into modern usage.

Initially it meant 'a filament or thread', and over time it retained that core sense; derived adjective/verb senses (e.g., 'fibred' meaning 'having fibres' or 'made into fibres') are consistent with the original meaning.