卡 (kǎ) is the universal foreign-name character for any "ka/cas/kas" syllable (
卡车 "truck,"
卡片 "card,"
卡夫卡 "Kafka"), and
斯 (sī) is the universal closer for any final "-s" or "-th" sound. The same two-character stem appears inside dozens of longer transliterations:
拉斯维加斯 (Las Vegas),
卡斯特罗 (Castro),
卡斯帕 (Caspar),
道格拉斯 (Douglas).
