Hi,
Just discovered a useful thing, not sure how many are aware of it.
If you have an Apple ID, you should be able to register for free for the
Developer Program (this needs to be confirmed, it's been a while since I
did mine)
https://developer.apple.com/register
In the downloads area you can search for 'glossaries'
https://developer.apple.com/downloads/?name=glossaries
And download the iOS glossary for your language. It's a .dmg file, but
you can decompress it with 7-zip on a Linux/Windows machine.
Inside the package you'll find a lot of .lg files: they're actually .XML
files pretty easy to read, or use for a search. Example:
<TextItem>
<Description/>
<Position>STRING_ID</Position>
<TranslationSet>
<base loc="en">Original English String</base>
<tran loc="XX">Translation</tran>
</TranslationSet>
</TextItem>
Remember that these files are behind a login and Developer Agreement and
can't be shared publicly, but you're still free to use them to help you
with Firefox localization.
Francesco