"Zijn stem klinkt heel zwak."
Translation:His voice sounds very weak.
Stem is the same as English 'steven' (rhymes with seven), an archaic word from Old English 'stefn', sometimes a /fn/ would become /m/ as it has in Dutch.
I seem to recall reading steven (voice) somewhere in Chaucer. If so, I guess it found its way into Middle English before being superseded. I can't quite remember, but the context was to do with someone's strong singing voice. Perhaps somebody can help bring the detail back to mind.
The links between languages always give me a kick. The onomatopoeic klingt (sounds like) reminds me of the Irish verb cling (to jingle, ring, tinkle) and the English verb clink from Old English clincan (compare clynnan, clynian (to sound, resound), perhaps from Proto Indo European gleng (to sound) from PIE galos, glos (voice, cry) related to call and glossary