Uoeno

[Sarah]

UOENO is a corruption of the phrase You dont even know. Colloquial vernacular predominately used in the south eastern and central southern portions of the United States. It is an expression of someones lack of knowledge about a certain situation, circumstance, person, or matter. Can also refer to the degree that someone lacks knowledge concerning a situation, circumstance, person, or matter.

[Sonia]

You dont even know

[Mark Zuckerberg]

The author, MS3MY, above is the most correct in that there is not a direct correlation between this acronym/abbreviation and its pronounciation.
Yaint even know is what these letters sound like when spat in sequence; however, all of the definitions above are also correct.