I get it.
cotton to, idiom
1. Take a liking to, get along with, as in This dog doesn't cotton to strangers. Although this verbal phrase comes from the noun for the fabric, the semantic connection between these parts of speech is unclear. [Early 1800s]
2. Also, cotton on to. Come to understand, grasp, as in She didn't really cotton on to what I was saying. [Colloquial; early 1900s]
Took me awhile to find this important information.