Hi François
I have a suspicion that this is a symptom of a known stupid bug in the Course overview block. When it displays the overview of activities, it firstly check if the activity itself provide a string "activityoverview". If there is not such string, the block uses it's own string
$string['activityoverview'] = 'You have {$a}s that need attention';
where it fills the placeholder with the name of the module. This string is translated into French as
Vous avez des {$a}s qui requièrent votre attention
including the "s" after the placeholder. So the block puts the localized module name ("Journal" in your case) into that string followed by the "s" and it looks like "Journals".
The French language pack should be probably fixed as the "s" should not be there, I guess.
The silly thing is that it should not be in the English pack too, of course. Note that even in English, it is likely to produce incorrect plurals like "HotPotatos", "Glossarys" or "Quizs". Better alternatives would be
$string['activityoverview'] = 'You have {$a} modules that need attention';
or using the proper modulenameplural or so.
Note this has been partially addressed by MDL-38480 but MDL-36282 is still open. And looking at http://lang.moodle.org/local/amos/view.php?t=1383687123&v=2500&l=%2A&c=block_course_overview%2Cjournal&s=&d=activityoverview suggests there are other languages that have put the "s" after the placeholder incorrectly.