From Old English 'swift' (quick), from PIE *sweyp- (to swing) — speed was conceived as sweeping, curved movement.
Moving or capable of moving at high speed; happening quickly.
From Old English 'swift' meaning 'swift, quick,' from Proto-Germanic *swiftaz, from PIE *sweyp- (to turn, swing, bend). Swiftness was originally about sweeping, curving movement — like a bird in flight. Key roots: *sweyp- (PIE: "to turn