Likely related to Japanese 石 (ishi).
いそ • (iso)
- seashore
- (from Early Middle Japanese) → Proto-Ryukyuan: *iso
- Northern Ryukyuan:
- Northern Amami-Oshima: 磯 (isho)
- Southern Amami-Oshima: 磯 (isho /ʔìɕôˑ/)
- ⇒ Yoron: 磯端 (ishubata /ʔìɕùbàtà/) (< *iso-bata)
- Southern Ryukyuan:
- Miyako: 磯 (isu)
- Yaeyama: 磯 (ishu /ʔíɕú/)
- Yonaguni: 磯 (isu)