because one of the most well known steriods is dianabol, which is called d-bol for short. It should make plenty of sense now. I don't know who did it first, but superdrol is a similar structure, and so they chose a similar name. A lot of "natural" (useless) products are trying to live off of the glory days, and if you see it called whateverbol, you might think of that PH that you blew up on 5 years ago.
aka marketing.