I have seen several instructions for tying quilts that use the term "double knot". A double knot could be a "granny knot", which will not hold, or it could be a "square knot", which is much better. I recently had the task of removing granny knots from the fringes of many dozen double fleece blankets donated to our Linus chapter and re-tying the fringe with square knots. We were also given several small quilts tied with some odd knot I had never seen before that could be pulled out easily with bare fingers without even being washed. Another complete re-do was necessary.
For quilts I use a completely different knot that I have seen done on many Lutheran World Relief quilts and was also used by my Victorian aged grandmother. I have no idea what it is called and I can't find it on the internet, but it is my favorite. Rather than holding one end of the thread in one hand and the other end in the other hand to tie, the needle is used for manipulation of the thread in one of the hands. The result is a great knot and no cutting waste other than the small length left on the needle at the end of the run after doing many knots.