Louis  FORTIN dit LAGRANDEUR

Québec Généalogie - What is a 'dit/dite' name?  When the first settlers came to Québec from France it was a custom to add a 'dit' nickname to the surname. The English translation of 'dit' is 'said'. The Colonists of Nouvelle France added 'dit' names as distinguishers. A settler might have wanted to differentiate their family from their siblings by taking a 'dit' name that described the locale to which they had relocated. The acquiring of a 'dit' name might also be the result of a casual adoption, whereby the person wanted to honor the family who had raised them. Another reason was also to distinguish themselves by taking as a 'dit' name the town or village in France from which they originated. This custom ended around 1900 when people began using only one name, either the 'dit' nickname or their original surname.

Source: American-French Genealogical Society, Woonsocket, Rhode Island (www.afgs.org/ditnames/index1.html)

Louis was a Soldat du regiment de Carignan .
The soldat, or soldier, is the first military rank in the army, at the first level of military hierarchy.

Some of the first soldiers to set foot on Canadian soil were French or English men, hired by companies engaged in exploration or the fur trade. These companies were responsible for all costs associated with the soldiers: recruitment, overseas travel, equipment, maintenance and salary. The soldiers were responsible for protecting the expeditions and their interests.
Source: tfcq.ca

A Soldier's Tale: Life as a Soldat in 18th Century New France