Triprayar temple is situated on the bank of river Theevra. Theevra river is also called Purayar. Hence this place got the name Thirupurayar (sacred river) and later became Triprayar. There is an interesting legend about the origin of this river. Lord Mahavishnu during his Vamana incarnation visited this place while going to Thrikkakkara and he found no water to wash his legs as the whole place was dry and desolate. Vamana took the water from his kamandalu (a small round vessel used by hindu sages to carry water) and poured the water to wash his legs, that source of water never went dry but kept on flowing as the Thiru Purayar or the Thriprayar (river of divine source) as it is called now. Purayar is also called Sreepriya river and Nandiyar.