Short for "cool head." In the late 1960's through the middle 1970's, anyone who was called a "cool head" or just a "head," was an intense party person. (Southern
California)They may have only been into one substance (pot) or the entire gamut. Therefore the name, "head shops" on the west coast. What
people would call a "smoke shop" today. They use to be the Disneyland for stoners, but no more.
Because of law enforcement efforts to put these
people in jail, code words were used to protect your allies. Nothing has changed.