商 was originally the name of the Shang Dynasty (商朝, c. 1600-1046 BC). After the dynasty fell, Shang people became traders, and 商 came to mean 'commerce' — one of the earliest recorded examples of a proper noun becoming a common word.
Components
ideograph
商shāng
commerce; merchant; Shang dynasty
Single fused 11-stroke unit that doesn't decompose into productive sub-components. Functions as one indivisible shape carrying the 'commerce' meaning — a later semantic borrowing after the Shang fell and trader descendants were called 商人. Filed under Kangxi #30 口 (kǒu) by tradition, with no visible 口-element surviving as a separable piece.
Filed under radical 口 (kǒu, #30) by convention. 口 is not a separate component in 商, so no strokes are highlighted.