Peen \Peen\ (p[=e]n), n. [Cf. G. pinne pane of a hammer.]
(a) A round-edged, or hemispherical, end to the head of a
hammer or sledge, used to stretch or bend metal by
indentation.
(b) The sharp-edged end of the head of a mason's hammer.
[Spelt also pane, pein, and piend.]
[1913 Webster]