I realize this question is old, just been going through the records for Nicolas. Where his ''dit Despatis'' comes from I don't know, but he is called Nicolas Froget dit Despatis on his marriage contract in 1652 already. And that is not a typo, the name was written Froget and not Forget.
Possibly he came as a soldier to the colony, which was one frequent way that men received a dit name. I have found no evidence for this though. He is from the city of Alençon in Normandie.
An explanation of the name Despatis: (contraction de «des patis»; signifiant «des pâturages» dans le Sud-Ouest). http://lequebecunehistoiredefamille.com/capsule/forget/genealogie