The 420 name can be traced back to the 1970s when it was used by a group of high school students in California as a cipher to get together after school and smoke marijuana. The term became a commonly used symbol of marijuana use over time via pop culture, music, and media. Nowadays, even April 20 (4/20) an informal celebration of the culture of cannabis is associated with it. The parents ought to be aware that it mentions drug-related behaviour. Know more about what does 420 friendly mean
Source: Saferloop