Mike, Your research sounds very interesting. I think this could warrant a new thread on the list, I'll let you choose a new subject. Notify me at firstname.lastname@example.org of your new posting.
Now to answer your questions (and also correct one of my earlier statement regarding the origin of the name Mortier): In my research on the name Mortier, I never came across a connection with death ("mort" in french). As far as the origin of the name: Surnames were given around the 12th century in Europe, as an important population growth (less wars or crusades, less epidemics) made it difficult to differentiate between the Jeans, Pierres and other Louis in the same village. Surname were built around an individual's occupation, place of abode, color of hair or other physical traits. In ancient french, a Mortier is a muddy pond, swamp or humid tract of land. (source:http://www.geneanet.org/onomastique/index.php3?nom=mortier&lang=frhttp://www.geneanet.org/onomastique/index.php3?nom=mortier&lang=fr) Jean de Mortier or du Mortier was the original spelling, with the particle dropping several centuries later in most cases. I think that Mortier (canons) were invented later, which would dismiss that as a possible surname's origin. The french institute for cartography (Institut Geographique National) has listed about 2 millions names of place in France, of which 356 bear the name Mortier, and another 162 some sort of variation (mortiers, mortiere,...), see: http://www.ign.fr/fr/GP/toponymes/bdnyme?TOPONYME=mortierhttp://www.ign.fr/fr/GP/toponymes/bdnyme?TOPONYME=mortier Those places are mainly concentrated in the Ouest part of France, just right of Britanny: departments 49, 37, 44 and 72. There is also a lesser concentration in the North, department 59 (Nord - Pas de Calais, Picardie region) The surname Mortier is quite popular in France: Between 1891 and 1990, 5592 persons bearing the surname were born in France. It is interesting to note that most of these birth were indeed in the departments 44 or 59 (Loire Atlantique, Nord) at a time when mobility wasn't as important as it is today. Source: http://www.genealogy.tm.fr/http://www.genealogy.tm.fr/
Coming back to Newfoundland: In the new world, places were named after natural caracteristics, people's name or people's place of origin in the old world, when not keeping their native name. For example the city of Detroit, in french meaning narrows, or Paris in Texas I guess was named after a person from Paris, France? The presence of cannons nearby would have most likely left a name of "Fort", "Redoute" or ... Garrison Point rather than Mortier.
I think the most likely origin of the name is that mysterious captain (I'll email you my source's contact off list).
I like the story about the headstone. What meaning under this charade? Ha, another french word :-) Keep me informed, Thanks.