1 a metal or plastic cap, usu. with a closed end, worn to protect the finger and push the needle in sewing.
2 Mech. a short metal tube or ferrule etc.
3 Naut. a metal ring concave on the outside and fitting in a loop of spliced rope to prevent chafing.
Etymology: OE thymel (as THUMB, -LE(1))
Useful english dictionary. 2012.