This paper proposes new origins for tense vowels in Tangut by integrating textual analysis of Tangut texts with comparative data from both Gyalrongic and other Sino-Tibetan languages. It uncovers two previously unreported sources of vowel tensing in compounding: the collective prefix (*S-) and the compound linker (*-S-). Both morphemes left only a few traces, indicating their antiquity and productivity in earlier stages. The collective *S- could be an inherited morpheme which finds parallels in Tibetan, whereas the compound linker *-S- emerged as a stage of morphological merging in West Gyalrongic with (an) obscure origin(s). These findings not only advance our understanding of the origins of Tangut tense vowels but also offer insights into Sino-Tibetan nominal morphology.
