The other day I was fiddling around with sketches, and I wondered if I made an ankh using a half-circle and a triangle made out of two 3 x 4 x 5 right triangles how it would look. My sketch looked better than the design I came up with, so I must be bad at guestimaiting what kind of triangles I use. Actually, I often find that the designs I come up with which appear to use circles, squares and triangles in my sketches look wrong when I use Inkscape to make geometrically accurate circles, squares and triangles.
Once I saw that the loop wasn't going to work with pure circles and triangles, I reworked it by tweaking the spline-points on a regular circle and then finding a triangle that fit the loop and used it as the serifs for the ankh's arms.
During the process of moving thick-lined polygons around, designing the arms to be hollow suggested itself, and I ran with it.