'stiff-stemmed' is an English compound formed from the adjective 'stiff' + the noun 'stem' with the adjectival suffix '-ed' to indicate 'having stems that are stiff.'

'stiff' comes from Old English 'stīf' meaning 'rigid, firm' (from Proto-Germanic *stīfaz), and 'stem' comes from Old English 'stema/stefn' meaning 'the stalk of a plant'; the modern compound 'stiff-stemmed' is a straightforward combination of these elements in Modern English.

The components originally referred to 'rigid' (stiff) and 'plant stalk' (stem); combined as 'stiff-stemmed' the meaning has remained descriptive, denoting plants with rigid stems.