This is the 4515th most frequent Japanese word.
小岩
"Small rock" or "pebble."
Here, '小岩' refers to an actual physical small rock that is rolling by the roadside.
道端に小岩が転がっていた。
A small rock was lying by the roadside.
In this context, '小岩' is used as a surname, indicating a proper noun.
彼の名前は小岩さんです。
His name is Mr. Koiwa.
In this sentence, '小岩' denotes a specific landmark rock that is a tourist attraction.