Konnichiwa Dotcomfool-san!
Yes, you find out a good point. "Rei" is a one word now, but this word is made of two words originally.
The upper part Kanji is a "Ame" and means "rain" in English. But this Kanji is an abbreviation and is "Rei" originally. This "Rei" is different from "Rei" that means "spirit". This original "Rei" means
the advent of a god(but it means "descent" in literal translation).
And bottom part Kanji is an abbreviation and is "Miko" originally. "Miko" means "shrine maiden" in English.
The first(white) word "Rei" express a shrine maiden with the advent of a god on her overhead.
In Japan, people had believed that shrine maiden can be possessed by a elemental spirit. "Elemental spirit" is synonymous with "god" in Japan. And shrine maiden told god's intention. It's similar to the Delphic oracle in Europe.
"Elemental spirit" is "Sei-rei" in Japanese and Japanese shrine maiden conceive a "god". In the West, the Virgin Mary conceive a Christ by the Holy Spirit. And "the Holy Spirit" is "Sei-rei" in Japanese.

But "the Holy Spirit" is used different Kanji from "Elemental spirit".
NANGI