The oldest shape behind 主 is not explained in exactly the same way by every scholar. A widely cited interpretation sees a small flame or lamp wick above its support — the source of later 炷, “wick”. Other early ritual interpretations have also been proposed. By the classical period, 主 was firmly used for what is central or in charge, including a master, owner or host. This sketch follows the lamp interpretation while keeping the claim cautious.
A piece of culture
The host and the heart of a place 主人 can mean the host who welcomes a guest, but also the owner or master of a place. Put it beside 客人 and you have the two roles around a shared table. 主 is also a useful building block in modern words: 主要 means “main” or “principal”, and 主意 means an idea or decision. One small character connects hospitality with the person or thing at the centre.