'smooth-margined' originates from English, specifically the combination of the adjective 'smooth' + the noun 'margin' with the adjectival suffix '-ed' to indicate 'having a margin that is smooth'.

'smooth' comes from Old English 'smōth' meaning 'even, without roughness'; 'margin' comes from Latin 'margo' via Old French 'marge'; the compound 'smooth-margined' is a modern English descriptive compound formed by joining these elements.

Initially, the components meant 'even, not rough' (smooth) and 'edge, border' (margin); combined as a compound they have long meant 'having a smooth edge' and this specific botanical sense has remained stable.