[maybevain]

I think the origin might be ”[ter]minal file [e]xplorer”, though the author might correct me here.

”Tere” is also, perhaps unsurprisingly, used in Finnish.

[mgunyho]

I would say that terminal explorer is what I had in mind initially (and incidentally, I also speak Finnish, heh). But a misspelling of tree is certainly a valid interpretation as well :)