For instance "goodbye" is said to arise from the archaic, " God be with ye " and is more likely connected with the " bye and bye' which means " some time again " , which I find more satisfying in that they will find they are surrounded with goodness until we meet again.
It meets the likeness of " farewell " or " fare thee well " that implies leaving, but in doing so that "wellness be your fare", a blessing that follows you where ever you go, your fare abundant.
And goodbye is sister to " au revoir " that recognizes that we will see one another or re-see one another again in the bye and bye. It means " Adieu, also that dieu follow you.
Each phrase imparts sentiment and good will that is expansed to one another and more than you think. Be careful what you say. Language counts.