The 'surface' group
The second noun refers to a part of something, and the first noun indicates what it is a part of.
barrel (gun) base (bed) bed (sea) bottom (valley) bottoms (pyjama) butt (rifle) butt (cigarette) core face (cliff) head (screw/flower) leg (table) lining peelings rind (lemon) rind (bacon) shaft skin stalk stump (tree) surface stub (cigarette) stub (ticket) stub (cheque) trunk
Standing by the doors, she looked down and saw a cigarette butt on the garage floor.
This oil is distilled from the flower head of an evergreen tree from Madagascar.
I stubbed my toes against a table leg and felt the pain and bit back the cry.
Doctors have discovered that dressings made from boiled potato peelings help burns to heal faster.
The road surface remained damp from overnight mists.
A cut rope dangled from a tree trunk where the other canoe had been tethered.