Yo - two letters, and an app premise so initially silly it makes even veteran yo-er Xzibit hesitate. But we can explain. (Via Know Your Meme)
Yo is an app that does exactly what it says on the tin. Press button, send a "yo" message to someone on your contacts list.
It took developer Or Arbel eight hours to code. According to ThinkProgress, it's so simple, Apple rejected it from the app store the first time around because the quality assurance guys thought it was unfinished.
"Arbel, who built the app three months ago, has quit his job and moved halfway around the world - from his native Israel to San Francisco - to work on Yo full time. He's opening an office, hiring staff and seeking 'strategic partners.' And oh yeah: He's already raised $1 million from investors."
That's a valuation of $125,000 per hour for the code that went into it.
Now, some 50,000 users have sent a combined 4 million Yos since the app went live in April.
There is some potential for an app whose only function is push notification. Twitter user Ryan Hoover posted this screen grab showing how users can receive a Yo every time a goal is scored during the World Cup.
And a writer for Time says it could be a welcome break from the current onslaught of privacy-invading apps.
"The new app ... doesn't require you to sign up via Facebook. It doesn't try to hoard your data to later serve you ads (yet). It doesn't offer voice calling or disappearing images or the ability to send people smells."
You can find the app in the iOS and Android app stores. And YO guessed it - it's free.