lu*pine (lú:pain) adj. of or resembling a wolf [fr. L. lupinus, lupinum]

Frá Wikipedia:
Another tradition relates that Romulus and Remus were suckled by a wolf, has been explained by the suggestion that Larentia was called lupa (courtesan, literally she- wolf) on account of her immoral character (Livy i. 4; Ovid, Fasti, iii. 55).

Name etymology

This character's name is a clear example of Rowling's use of descriptive names for her characters, settings and other story elements. His first name, " Remus", is an allusion to Romulus and Remus, the legendary twin founders of Rome, who as infants were cared for by a she- wolf.

His last name, " Lupin“, recalls the English word ” lupine“ (meaning ”characteristic of or relating to wolves"), which in turn is derived from Latin lupus (" wolf"). In the folklore of northern France, lupin is also the term used to refer to a type of werewolf, noted for its shyness (in contrast to the more aggressive and violent loup-garou).

His middle name, John, means “God is gracious”.