I came across this knot when it was used to tie a guy wire to a newly purchased light weight tent. I am reasonably knot savvy but have never come across it. It forms a non-slip loop when pulled up tight and is easy to tie.
I checked the Ashley Book of Knots, and as #1044 I find your knot.
A very compact loop tied with a bight, for use in the end only.
It does not have a name in that book but may have been named by someone since the book was finished in 1939, or published in 1944. Or even before, as even as careful as Clifford W. Ashley was, he did miss some names.
(As I did use a paper book I do not have a link for you.)
It is not, as now again suggested in an other answer, the Alpine butterfly. That knot has some similarity and will do the same kind of jobs, likely better. But it is a different knot.
Alpine Butterfly Knot.
Here's a how to tie for yourself.