"Eighty holes in your shirt, there: your own Jamaican clothes." In 2009, computer programmer Tom Lehman was confused by that line in Cam'ron's rap song "Family Ties." His search for an explanation would lead him and his friends to create a service that now draws millions of visitors a month—and has won the backing of stars and a big venture investor.  Mr. Lehman, now 29, started out by asking his former Yale University classmate—Mahbod Moghadam, who had just left a corporate-law job—what the lyric...  "Eighty holes in your shirt, there: your own Jamaican clothes." In 2009, computer programmer Tom Lehman was confused by that line in Cam'ron's rap song "Family Ties." His search for an explanation would lead him and his friends to create a service that now draws millions of visitors a month—and has won the backing of stars and a big venture investor.  Mr. Lehman, now 29, started out by asking his former Yale University classmate— Mahbod Moghadam, who had just left a corporate-law job—what the lyric meant. Mr. Moghadam, now 30, said the holes referred to the tattered clothing of impoverished Jamaicans. The two decided to start a blog that would explain the lyrics from Cam'ron's "Purple Haze" album, teaming up with a Yale classmate, Google project manager Ilan Zechory, now 29. It expanded to other singers and poets, and many of their classmates started contributing.  The site's standout feature was how it let users annotate texts. Contributors could highlight a line or word, and type in an explanation. When other users clicked on the highlighted portion, the explanation would pop up in a box.  The trio realized the blog, called Rap Genius, had much bigger potential when they allowed the wider public to contribute song explanations in the summer of 2010. By mid-2011, the site surpassed one million unique hits per month, with users reading and rating other people's annotations, and adding comments of their own. "Gradually, we started to get the idea that this was a generic platform that was good for all kinds of text," from Supreme Court cases to the Bible to shareholder letters, Mr. Lehman says.  They decided to make a go of it as a business, and things moved quickly. Rap Genius got an investment of $170,000 from Silicon Valley startup incubator Y-Combinator, and later attracted celebrity investors like actor Ashton Kutcher and rapper Nas, as well as venture-capital firm Andreessen Horowitz, which contributed $15 million. The trio's company, Genius Media Group Inc., launched a literary offshoot, Poetry Genius, which has proved especially popular with teachers, and News Genius for explaining news articles.  The original site has more than doubled its traffic in the past year to 4.9 million unique visitors a month, according to comScore, and has grown to 25 employees. Rap Genius isn't generating revenue, but Mr. Moghadam says the site may eventually consider targeted ads and corporate partnerships. For now, among other things, Rap Genius hopes to expand into the art world with Art Genius, which will allow users to trace a section of a piece of art and offer an interpretation.  Many rappers now have verified accounts on the site and explain their own lyrics through videos. Cam'Ron ended up submitting his own explanation for "Family Ties": The holes actually refer to the popularity of mesh tank tops in Jamaica.
A question about a song led to the creation of Rap Genius—a site with millions of visitors and some big backers.