Self referential abbreviation, but has a double meaning derived from two seperate cultural contexts.
1. In Pakistan, and possibly several other Commonwealth countries that derive their legal and penal systems and classifications from the British system, the legal section code 420 refers to a case classified under a fraud or fraudelent activity. Thus someone that is branded or associated with this number will be be thought of as devious, cunning, willing to partake in illegal activities, sinister and capable and likely to cause harm to others. Depending on context in which the number is mentioned, it could lend a humorous or serious connotation to whatever person or object it is used to describe.
2. In the U.S. this number represents a date, in Particular the 20th of April of every year. This day is widely acknowledged as a day for the celebration of Marijuana and the culture that is asociated with it. In some cases, it may refer to the time of the day, namely 1630 hours, or twenty past four, at which time it is generally assumed fit for smoking (marijuana). In such cases, as in the example below, the time does not have to be twenty past four, the general understanding being that if someone is to refer to the time being fourtoooh, then it is a good time to smoke a joint.
a) At first s/he seemed trustworthy, but lately s/he seems a bit fourtoooh.
b) Call him, ask him if he can make it. Tell him if he doesnt show up we'll have to go fourtoooh on his ass.
Guy: "What time is it?"
Stoner: "Fourtoooh man! lets spark one"