thick arm; brawny arm
Describes a physically large, muscular, or thick arm. Often used in descriptions of strength or physical build.
彼は太い腕で重い荷物を軽々と持ち上げた。
He easily lifted the heavy luggage with his thick arms.
そのレスラーは太い腕を自慢している。
That wrestler is proud of his brawny arms.
Compound of 太い (thick) + 腕 (arm). The reading ふというで is a straightforward combination of the two words.