Where does “皆さま” come from?

皆さま (Japanese) comes from Japanese 様, from Middle Chinese 樣.

皆さま (Japanese): everybody, everyone

Definitions

Step	Language	Word	Meaning
1	Japanese	様	way, style, appearance; be like, look like, seem...
2	Middle Chinese	樣	—

皆さま — Etymology, Origin & Word History | Etymology Explorer