Interesting Behavior

I have no clue as to why my cat does this. She doesn't do it very often
anymore but sometimes she'll curl into a ball, begin sucking/licking on
the tip of her tail while kneading the area right around it, while
purring loudly.

As best as I can tell she's predominantly silver tabby with some orange.

Aside from that she's incredibly smart and cuddly. Is this some kind of
behavior she maybe remembers from nursing?