macos – What phrases are saved in `~/Library/Spelling/en`?

John Gruber lately tweeted on Mastodon:

Considered one of my favourite options on the Mac […] is including new phrases to the system-wide spelling dictionary. The characteristic dates again to Mac OS X 10.0 and I am fairly positive was in NeXTStep a decade earlier than that.

And, even higher, the customized phrases you add to the dictionary are saved in a easy textual content file, one phrase per line, at:

~/Library/Group Containers/group.com.apple.AppleSpell/Library/Spelling/LocalDictionary

https://mastodon.social/@gruber/112560468582323979

In my case, the file is definitely at ~/Library/Spelling/LocalDictionary, as a result of I am loopy and run an historical model of macOS (10.9 Mavericks). I do not suppose that is related to the remainder of my query.

After taking a peek at LocalDictionary, one thing caught my consideration. ~/Library/Spelling/ comprises one other textual content file, en, which like localdictionary comprises one phrase per line. These phrases are totally different from those in localdictionary, however like locationdictionary they appear like issues I in all probability typed over the previous few years and wished spellcheck to study. For instance, it comprises the title of the group I work for, and a few individuals I do know with uncommon first names.

What is that this en file, and the way is it populated? Why do some phrases find yourself in en whereas others find yourself in LocalDictionary?

(I assume that on fashionable macOS, the equal file is situated in ~/Library/Group Containers/group.com.apple.AppleSpell/Library/Spelling/en)