observance
‘the act of observing’
Lexical development traced from the Tamil root:
E. obscherwance, obseruaunce, obserwans, obseruanc, obcervaunce, obseruawnce, observawns < O.F. observance, osservance ‘observance, discipline’ < Lat. observantia ‘act of keeping customs, attention, respect, regard, reverence’ < observantem < observare ‘watch over, note, heed, look to, attend to, guard, regard, comply with’ < ob ‘in front of, before’ + servare ‘to watch, keep safe’ < zuhv < ser- < Tamil iṟai