house snake
/ˈhaʊs ˌsneɪk/noun
1Specifically. Any of several North American colubrid snakes of the genera Elaphe and Lampropeltis, especially the milk snake, L. triangulum.
2Specifically. Any of several small, non-venomous African colubrid snakes of the genus Lamprophis (formerly Boaedon).
3A snake believed to protect or watch over a household, especially one kept as a household god.
Origin
Early 17th century (in an earlier sense). From house + snake.