This is from the children song "Compère Guilleri":
Il était un p'tit homme
Appelé Guilleri,
Carabi,
Il s'en fut à la chasse,
A la chasse aux perdrix,
Carabi
Titi carabi, Toto carabo,
Compère guilleri.
Te lairas-tu, te lairas-tu,
Te lairas-tu mouri.
How should I understand "en" and "mouri" grammatically?
I know that "en" may work in different ways (adverb, preposition, pronoun etc), but I'm not sure what's happening in this case.
About "mouri", I guess it's supposed to mean the infinitive "mourir", so where's the final "r"?

