斯密斯 is an older / Hong Kong-influenced rendering of 'Smith'; the modern mainland standard is
史密斯 (Shǐmìsī).
亚当·
斯密 (Adam Smith, the economist) is sometimes spelled this older way in older economics translations. The chars are purely phonetic:
斯 (sī) for 'S-',
密 (mì) for '-mi-',
斯 again for '-th'.
