From Proto-Southwestern Tai *zaːjᴬ (“sand”), from Proto-Tai *zwɯəjᴬ (“sand”), from Old Chinese 沙 (, “ *sraːl, *sraːlssand”). Cognate with Lao ຊາຍ (sāi), Shan သၢႆး (saay4), Ahom 𑜏𑜩 (say) or 𑜏𑜩𑜤 (sayu), Zhuang saiz.
This word was written ซาย (saai) (with a ซ (sɔɔ) initial) in documents prior to the 18th century, but shifted to the current spelling (with a cluster ทร initial) during the 18–19th centuries, possibly under the popular misconception that this word was of Khmer origin, and that the s- initial had developed from an earlier *dr-.
d r ā y
z ā y
ทราย • (saai)