What does "All things X" mean?
Solution 1:
FTR,
Is the expression "All things X" a parody of some other popular phrase,
Not really. Traditionally it is an "old-fashioned sounding" phrase.
The phrase has, let us say, "dignity" and "charm".
As Morton mentions, there is a Church Song "All things bright and beautiful."
Traditionally, you would use the phrase it for shop names such as - let's say -
All things lace. (wedding gowns!)
All things gentle. (they sell kittens!)
And so on.
IF you use it for something modern or fun, like "All things gym" or "All things data": it's not really a parody, it's more just a slight twist.
The form "All things ___" is usually used for more old-fashioned, dignified things: it's rather cute, a twist, to say "All things disco" or "All things data". Not really a parody though. Just a slight smile.
or does it have its own meaning? Or is it just a misuse of grammar?
It's not a misuse of grammar. It has a clear and direct meaning.
Consider a similar phrase to "All things _____": you will occasionally see shops named "The Compleat ____" (With that archaic spelling.) For example, "The Compleat Watchmaker" or "The Compleat Knitter". In this case it's a reference to an old book "The Compleat Angler." My point is that "All things ____" is a phrase that traditionally sounds, err, traditional - dignified - "old-fashioned". There are a couple of phrases like this in English, where you substitute in the word of your choosing.
{A more extreme, indeed openly humorous, example is "Ye Olde ____". So, "Ye Olde Bake Shop" and so on.}
Unfortunately I have absolutely no idea where "All things ____" originated. Perhaps, from the church song title, "All things bright and beautiful," which is a Victorian hymm (the epitome of Victorian hymms :) ), written in 1848.
All things bright and beautiful,
All creatures great and small,
All things wise and wonderful,
The Lord God made them all.
Regardless of the origin, "All things _____" is, yes, a catchphrase in English.
Traditionally you'd put something dignified and old-fashioned in there (like "knitting," say): putting in something modern is just a slight smile, not a parody.
Solution 2:
Obviously the roots are very old, but it's a current trend in naming tech companies or blogs.
Main example was a very influential tech blog AllThingsD (2003-2013) by Kara Swisher and Walt Mossberg. As in "All Things Digital".
Is the expression "All things X" a parody of some other popular phrase
Not a parody, but copycat.
Solution 3:
The meaning of "All things X" depends on the context. Here are a few examples:
Pinpointing stars in the sky makes all the difference. This is why Gaia is having a sensational effect on all things astronomy.
Here, "all things astronomy" means "all branches of astronomy".
"This guy consumes all things baseball. There is not a lot else going on in his world."
Here, "all things baseball" means "everything related to baseball".
The expression "all things leather" doesn't simply mean "everything related to or made out of leather" but it is also used to include perceived luxury objects that are unnecessarily made out of leather like:
- hand-stitched natural leather cooler covers
- leather bucket
- leather eye glasses