Please add to the Comments section below the context in which you encountered this word.
Kaya nabaliw si Menangge dahil naabutan pa niya nang undayan ng saksak ni Uro ang kanyang bunso.
In-agnay is the snake who dwells close to the Undayan (bottom or base of the earth).
The Mandaya also tell of a Great Flood that destroys all inhabitants except one pregnant woman who bears a son named Undayan.
