Seriously speaking, I did. Last year I had problems with my hip flexors. Even think I had a mild sprain on the right after doing grande battements. And o'boy are they always cramped so tight. Realised at somepoint that it could my hip flexor were not warm enough for the big movements. So tried doing some preclass warm ups for those. And it worked. But being a bit lazy an idea for warm up gear just kept haunting me.
So The Jämäballerinas (= leftover ballerinas) were made. Used up some stashed left over yarn for these. Hence the name.