History of the L'Enfant Family Name
L'Enfant is an Acadian name www.acadian-cajun.com/genac5.htm - The Acadians were French settlers of eastern Canada (Nova Scotia) who were exiled from their land in the 1750s during the Anglo-French struggle for North America. Between 1755-63 most of the Acadians were deported to the American Colonies, Great Britain and France. See also www.acadian.org.
Sometimes a person would take on another name, based on where they were from, their job, a friend or relative's name, etc. One case in which this happened is with Roger Caissy. Some of his descendants used the surname Caissy dit Roger. Somewhere down the line, some of his descendants used the Roger part and just disregarded the Caissy part. So you have the Cajun surname Roger that actually descends from Caissy. Other descendants continued using the Caissy name. Bob Quintin wrote a book on the subject, The "Dit" Name: French-Canadian Surnames -- Aliases, Adulterations, and Anglicizations in 1993. It covers 33,000+ dit names. It also talks about how some French names were turned into their English equivalents ... LeBlanc became White, Doiron became Gold, etc.
Here's an example from Pallot's Marriage Index for England 1780 - 1837.