interesting

The "good", in the expression"good-bye", is nothing about with "good" or "bom". This expression is one eufemismo for "God", because some people can't say the god name for other things, just when they can say about "God" , so we use, or write "good" to prevent say "God". The origin the expression is a kind os the sentence "God Be with You" , and "you" before was writing "ye". the complete sentence is "God be with you" was normal in the Shakespeare's time. and with the time the people started duplicated the "bye" and stayed "bye-bye".

This also happens in Portuguese, some times we hear somebody to say " tchau-tchau". They say two times, when one would be enough! But at last, language is language and use is use! Ah, In century XV it was common also to say " Godspeed! " as a farewell form, " would be equivalent to ours; Deus abençoe vc" , " Deus te dê muita prosperidade", etc...