ADIEU, BYE-BYE, CHEERIO: THE ABC OF LEAVE-TAKING TERMS IN ENGLISH LANGUAGE HISTORY
The article gives a chronological overview of the leave-taking terms in English language history. In a second approach the leave-taking terms are classified according to the motivation that is the basis for a specific coinage. Expressive expressions, wishes for God’s protection and wishes for a good time or health are shown to be especially prominent. Furthermore, there are a few loan expressions. The article also tries to explain words and phrases whose origin is unclear: "73" is shown to be an unmotivated, accidental Morse expression; "So long" is considered a Norwegian loan translation; evidence is given to see the origin "Good-bye" in the phrase "God buy you". It also shows that many phrases become phonetically reduced (and opaque) and/or semantically "void", which forces the speech community (or particular groups to invent new phrases.
... We still have Fr. "adieu" = "to God", It. "addio" (dito), Sp. "adios" (dito), G.dial. "Grüß Gott" = "may God greet [you]".