I am trying to find a a resource that provides English/French translations for GIS terminology. Obviously I could use Google or a French/English dictionary, but there are many cases where there are multiple French words. For example, the word layer could be translated as couche (which seems to be the most common translation), or strate (which is a geology term and may be more pertinent when talking about GIS)
GeoServer (and many other open source projects) have internationalisation efforts that could help you with this. For example if you compare https://github.com/geoserver/geoserver/blob/master/src/web/core/src/main/resources/GeoServerApplication.properties and https://github.com/geoserver/geoserver/blob/master/src/web/core/src/main/resources/GeoServerApplication_fr.properties you will see that the English "Layer(s)" is translated as "Couche(s)".
I have never tried (as my language skills would hinder rather than help) but I believe that Transifex allows you to see two languages side by side.
The GeoServer user guide is also translated in to French (and other languages) which could help you. I can't find a link but I think it shows up if your locale is set to FR.