I always thought that the expression "high five" is spelled "half five". What a dumb ass I am. Now that I know the spelling - the phrase finally makes sense to me! I am now also pretty sure I have heard the phrase "low five" - which should have triggered a review in my head about my inner "half five" notation.
Mini word play epiphany:
Context: My friend is about to return to the Bay
They: I miss home, it sucks here
Me: Welcome back
Alternative: Well, come back!