Camus loved the sea and nature generally. His unfinished early novel La
Mort heureuse contains a scene in which Patrice Mersault goes swimming in
the sea; the scene is described in very sensuous terms. (See Albert
Camus, La Mort heureuse, Le bain de
mer, in French.)
So on a very literal level, Mersault can be read as mer (sea) and
sault/saut (jump; the 'l' in
'sault' is silent); when ignoring that French creates compounds in a
very different way than English, the name can be read as "jump into the
sea" (French equivalent: "saut à la mer").
After abandoning La Mort heureuse, Camus started working on
L'étranger. He reused elements from La Mort heureuse, but
obviously changed many other things, including the narrative
perspective (the third person narrative was replaced with a
first person narrative). The change from Mersault to Meursault leads to
a name that actually already existed:
Meursault is the name of a
commune in France (now familiar to anyone who has watched the 1966 film La Grande
Vadrouille).
The change also introduces a wordplay: "meur" sounds like "meurs" and
"meurt", which are singular forms of the present indicative of the verb
mourir. From this point of
view, Meursault "jumps" to his death by killing the Arab in the first
part of the novel.
In Looking for the Stranger (University of Chicago Press, 2016), Alice Kaplan presents the following story about how the name change may have come about (page 65-66):
In the only surviving manuscript of the novel, (...), Camus still
spells his narrator's last name "Mersault", identical to the hero of A
Happy Death. Later, he would differentiate him from the main character
of A Happy Death, by adding the "u" to Meursault's name. When you
pronounce "Meursault" without the "u", it sounds ethnically Spanish,
like "Merso" (...).
(...) Some Camus experts claim he thought of the name change at a
dinner party where he was served the delicious and expensive white
Burgundy wine, Meursault. Whether or not the story about the Paris
dinner party is true, there is something more expected about the way
Meur-sault sounds to a French ear than Mer-sault, and the
coincidence might have pleased Camus since the extra "u"—signifying
meur (death)—served his novelistic purposes in every other way.
