Not French, but Norse. Have a look around Frances Coakley's site for boundless information on the Isle of Man. (She also offers a CD with more info...) http://www.isle-of-man.com/manxnotebook/http://www.isle-of-man.com/manxnotebook/
CORLETT (sometimes pronounced CURLEOD), is from the (O.N.) personal name Þorljótr, (the initial c representing the Celtic prefix Mac.) The word 1jótr means 'deformed,' or ' ugly,' but that can scarcely be its meaning in this compound. Dr. Vigfusson thinks that ljót is the same as the old Teutonic leðd, 'people.' It is not found by itself in the Landnámabóc, though, in combination with Þórr it is common there. In the Flateyjarbóc, written two centuries later, this compound name occurs twice. Ljótr is found on the cross in the old church-yard at Ballaugh in combination with Liut, as LIUTWOLF§.
'The name Thor has always been thought to sound well and is much used in proper names. Þorljótr is found in many runic stones in Denmark. The MACLEODS in Scotland have always claimed a Scandinavian origin and their name is probably from Mac ljótr, the Þor not having been inserted.'** "The MACLEODS of Cadboll and the MACLEODS of Lewis not only quarter the Manx trie cassyn (three legs,) but use the same motto quocunque jeceris stabit, which, I think, clearly points out that the chiefs of that name are descendants from the Norwegian sovereigns of Mann and the Isles, or some other Manx connection."++
In the parishes of Ballaugh and Lezayre nearly one fourth part of the population are CORLETTS. Compare (Welsh) LLOYD.
* Manx Note Book, No. 9, Pp. 11-12. ** Cleasby and Vigfusson, P. 743. ++Oswald, in Manx Society, Vo1. V., P. 7. [fpc - the useof the motto is not clear and I suspect incorrect - it only appeared in Mann on the Murrey Penny of 1688]