420: What Does It Mean? Where Does It Come From? the420times October 15, 2009 Medical Marijuana NewsApril 20, 2009 — What does 420 mean? Where does it come from? Read the article below to find out—you’ll be surprised!What 420 Means: The True Story Behind Stoners’ Favorite Number by Ryan GrimWarren Haynes, the Allman Brothers Band guitarist, routinely plays with the surviving members of the Grateful Dead, now touring as The Dead. He’s just finished a Dead show in Washington, D.C. and gets a pop quiz from the Huffington Post.Where does 420 come from?Read the full story at Huffingtonpost.com.