noun
strong arm; iron arm
Refers to a physically powerful arm or, by extension, a person with great strength or capability. Often used in compound expressions like 鉄腕アトム (Astro Boy) or 鉄腕投手 (iron-armed pitcher).
彼は鉄腕で知られる投手だ。
He is a pitcher known for his iron arm.
鉄腕アトムは手塚治虫の代表作です。
Astro Boy (literally 'Iron Arm Atom') is Osamu Tezuka's masterpiece.
剛腕 also means 'strong arm' but often implies a forceful, aggressive style, especially in sports or leadership, while 鉄腕 emphasizes sheer physical strength and durability.
Compound of 鉄 (iron) and 腕 (arm). The exact historical derivation is uncertain, but the word is conventionally associated with the idea of an arm as strong as iron.