名詞 peen:

1. the part of a hammerhead opposite the flat striking surface (may have various shapes)

peen

n.（名詞）
The end of a hammerhead opposite the flat striking surface, often wedge-shaped or ball-shaped and used for chipping, indenting, and metalworking.
錘頂：錘頭平的打擊面反面通常呈楔形或半球形的頂端，用于削、鑿和金屬加工
v.tr.（及物動詞）
peened,peen.ing,peens
To hammer, bend, or shape with a peen.
錘打：錘擊、使彎曲或用錘頂來打成一定形狀

來源：
[Probably of Scandinavian origin]
[可能源于斯堪的納維亞半島]