Punctuation Nomination

Given the architecture and visual plumage of the colon [:], why is the semicolon [;] so named?

Shouldn't the period [.] be the true semicolon [;], since it is half as many dots as the colon [:]?

Ergo, I hereby nominate the nomenclature of the comma [,] as the paraquasidemicolon.

(The disturbing thing is that I thought of this in my sleep, or semidemiquasisleep, last night.)