noun
Archaic term for the upper arm, contrasting with 二の腕 (forearm). Rare in modern Japanese; 上腕 (じょうわん) is the common modern equivalent.
See also: 二の腕
古い文献では、一の腕と二の腕を区別して記述している。
In old documents, a distinction is made between the upper arm and the forearm.