When you're looking at French-Canadian family trees, it doesn't take long before you run into people with names like "Jacques Choret dit LaFleur".
What's the whole 'dit' thing?
Basically, it comes down to a way of distinguishing different branches of families with the same surname. So, if you've got two clans of Chorets living in the same locality, one group might adopt a 'dit' name to make it clear which group they belong to. (Note that these clans needn't be related to each other at all.) 'Dit,' of course is from the French verb 'dire' (to say), so the obvious translation for "Choret dit LaFleur" is "Choret (that is to say) LaFleur" and generally that's the name you'd use when referring to someone conversationally: "Hey, did you hear what happened to Jacques LeFleur the other day?" - that sort of thing.
On official records though (baptismal, marriage, death, etc.) the actual family surname is used, though in many cases the 'dit' name often appears. Sometimes it's hyphenated, e.g, Choret-LaFleur.
What I've found is that they exist for a few generations and then get dropped. Occasionally, the reverse happens: the 'dit' name endures and the family name disappears. This has led to some degree of head-scratching on a few dead-ends (see the previous post on Ferdinand (né Tousignant) Vandreuil my great-great-grandfather).
Where do they come from? Interestingly, many seem to have been chosen from someone's military service: where the 'dit' name is the name of the company they served under, or sometimes their commander, the nom de guerre. Sometimes it's a placename, or related to a trade (both of which are common origins for family names as a whole). You'd think that this would make things a little easier, but consider that if everyone in a military company is using the same 'dit' name, then you end up with more confusion: for example, there are over 200 family names using the 'dit' name LaFleur!
About the only American equivalent I've seen to this would be the phrasing you hear among the upper classes, e.g., "the 'Greenwich' Barclays" (as opposed some other set of Barclays that don't live in Greenwich), but of course even in this case no Barclay would ever refer to themselves as 'Greenwich'.