人が集まる

This phrase combines '人' (hito, person/people) and '集まる' (atsumaru, to gather/collect). The concept of people gathering is fundamental and has likely existed since the earliest stages of the Japanese language. '人' is an ancient character, and '集まる' is a native Japanese verb. The phrase itself is a direct and descriptive way to express the action of people congregating, and its simplicity suggests a long history of use without significant etymological layers beyond the meanings of its constituent parts.