How to name a lot of point of a KML file?

Without any screenshot is hard to help you, but if you have i.e. Notepad ++ you can try to Replace all blank names with the name you want.

I guess, your .XML code looks now as:

         <Placemark>
        <name></name>

Then after Crtl+F click toggle Replace and replace it with name you want, like below:

Thereafter each point will have a name.

I finally found the solution: I imported my KML file to Excel opening it as a XML Table type file (the import made Excel load for a long time, but didn't crash). Then I could extract latitude and longitude data. I put them in a blank KML file that I created with Google Earth so this file was correctly formatted. Then I edited the "description" fields for each point, pulling my cells on Excel. Saving it in CSV, I can open it on Google Earth and save it in KML if I want.