'tough-stemmed' originates from Modern English, specifically the adjective 'tough' and the past-participle/adjectival form 'stemmed' derived from the noun 'stem', where 'tough' meant 'strong or durable' and 'stem' meant 'stalk or trunk'.

'tough' developed through Middle English (from forms like 'tough'/'togh') ultimately from Old English roots meaning 'strong'; 'stem' comes from Old English (e.g. 'stefn'/'stamm') and Proto-Germanic *stamną meaning 'trunk, stalk'. The compound adjective 'tough-stemmed' was formed in modern botanical English by combining these elements.

Initially it meant 'having stems that are tough (durable)', and this literal botanical meaning has largely remained the same in modern usage.