Cotton is a fiber (from the cotton plant). Flannel is a finish or weave. Hence you can have flannel wool as well as cotton flannel - i.e wool made with flannel finish or cotton made with flannel finish. Hope this helops.
A very memorable song from Joni Mitchell that featured the line They paved paradise and put up a parking lot.. This best described places I remember growing up in Bloomington, MN in my teens where numerous places were torn down, most notably a restaurant I frequented that was replaced with a Park and Ride lot.
In France they are called 'papillon.' Parking tickets are called 'papillon' too, because they are big pieces of yellow paper. When they are placed under a windshield wiper they flap like a big yellow butterfly. The Sioux Indians called butterflies 'fluttering wings'. There are other stories which are not as pleasant.