(A personalized black & yellow California state vanity license plate, customized to read “YOOO”, on the front of a Dodge car.)
YOOOO, WHAT UP?
So this one is obviously the loud greeting “Yo!” stretched out to four Os.
“Yo” enters English slang through multiple different channels! In historic Middle English, “yo” (or “io”) was used to get someone’s attention. It’s also present in Yiddish and AAVE. All the way back to Latin, “io” was an expression of joy and greeting (and they didn’t have the letter Y back then).
It’s hard to come up with any obvious alternate explanations, but if you stretch, you could also imagine it’s saying “Why? Ohhhhhhh” – like some dawning realization after asking something profound. I guess.
YOOOOOOOOOOOOOOOOOOO