KiCAD file name extensions a bit strange for solder mask and silk screen?

I was confused about the names KiCAD is using to generate the top and bottom silkscreen and solder masks.

For the silkscreen, *.gto or *.gbo is used, while for solder mask *.gts or *.gbs is used.

Isn’t that confusing? I was expecting to see *.gto or *.gbo for solder mask, since there’s an “o” in both the file name extension as well as in the term “soldermask”.

On the other hand, *.gts or *.gbs would be better placed for the silkscreen, because of the “s” in the file extension and the word “silkscreen” starting with an “s”.

Or is it just me finding this confusing?

Why did I pick up this item? Because I sent my PCB to FreeDFM for a check up (adviced by Chris Gammel in [this post] 1). After uploading the stuff, FreeDFM asked me to help identifying my files:

That looked a bit weird to me and then I saw that they were probably mixing the solder mask with the silkscreen layer. After my “investigation” I found out they didn’t make a mistake, but I was misleaded. Hence…

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Definitely confusing, but built upon convention I believe.

Solder Mask is also known as Solder Stop Mask, so thats where the g(erber)t(op)s(top) or *.gts comes from

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And silk-screen is referred to as “overlay” hence the “O” in file names.