Comparative evidence

sed

• Lat. sīdō -ere, perf. sēdī ‘sit down’, ‘squat’, ‘settle’, ‘subside’ (OLD: 1756) 

• Lat. sedeō -ēre ‘sit’, ‘be seated’, ‘be settled’, ‘rest’, ‘lie’, ‘stay still’, ‘sink’  (OLD: 1724-1725)

References

OLD = Glare, P. G. W. 1968. Oxford Latin Dictionary. Oxford: Clarendon Press.