Usage of the phrase " just because" at the end of sentences

grammaticality sentence-ends

Solution 1:

How? Just because...

Sorry, I couldn't resist. I don't have an ANSWER, but I have a theory. I think the phrase is verbal shorthand, that has no proper literary form. What I mean: I believe the phrase may have come from people saying "because... because..." not having a reason, then "just because!"

Solution 2:

The Urban Dictionary defines "just because" as meaning "because you could".

It's really just a 'circular' response:

I did it because I could do it (no other reason)
He did it because he could do it (no other reason)

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