According to Merriam-Webster's online dictionary, "yo" and its forerunner "io" have been around for hundreds of years:

Etymology: Middle English yo, io.

Yo is used especially to call attention, to indicate attentiveness, or to express affirmation.

Yo, you got that now, yo?
Institutional Memory | 12.27.06 - 10:23 am | #

"Mister Yo." It does have a kind of nice ring to it!
CaliforniaTeacherGuy | Homepage | 12.27.06 - 10:38 am | #

Good for you- er, I mean, yo.
Mrs T | Homepage | 12.27.06 - 3:20 pm | #

Wow. I had no idea Webster had already dealt with this.
NYC Educator | Homepage | 12.27.06 - 4:57 pm | #

What's wrong with trying to teach the kids standard English...that would just be way too hard for school boards to comprehend, yo.
Aisby | Homepage | 12.28.06 - 10:17 am | #

I absolutely teach standard English. I don't think that precludes kids talking like kids, though.
NYC Educator | Homepage | 12.28.06 - 11:50 am | #

And here I thought the origin was Japanese. One can add emphasis to a sentence, and call attention to new information in it in a casual setting by adding "yo" to the end, typically after a short form of the main verb.
bmagnus | Homepage | 12.28.06 - 2:24 pm | #

Remember, "yo" spelled backwards is "oy"!!
Ellie | 12.28.06 - 4:37 pm | #

As a NYK publik sckhool stiudint eye no furst hande thaet wee saye "yo" lots becuz owr edukation sysystem iz so badd, it dozn't tech us gramar good
LeftyHenry | Homepage | 12.29.06 - 7:02 pm | #

That was a riot, yo!
Ms. Cornelius | Homepage | 12.30.06 - 11:08 pm | #

Yes, but nothing was as annoying as uptalk -- which, thank God, seems to have died, like, ya know?
rightwingprof | Homepage | 01.04.07 - 12:49 pm | #