Decorated with or equipped with fillets (narrow bands used as ornaments or for binding).
From 'be-' prefix plus 'filleted', the past tense of 'fillet'. A fillet comes from Old French 'filet' (thread), derived from Latin 'filum'. The adjective form suggests something thoroughly adorned with these ribbon-like ornaments.
Medieval and Renaissance buildings were obsessed with fillets—thin decorative bands were used everywhere, from stonework to furniture to clothing—so 'befilleted' would have been a natural way to describe the ornate architectural details that made castles and cathedrals so visually complex.
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