The demoness Mahishi had received a boon from Brahma. She could only be killed by a son of Shiva and Vishnu.
Vishnu took the form of a woman, Mohini, and begat Ayyappa with Shiva. He grew up as Manikanda with King Rajasekhara.
Mohini is ‚the one who deceives‘, whose form Vishnu takes when necessary.
A name of Shiva is Hara, a name of Vishnu is Hari, together they are Harihara. Ayyappa is therefore also called Hariharaputra, where Putra means son.
Ayyappa’s mount is the tiger.