Where’s did the old saying 3/4 cam come from

Yeah like 4 of them, from mild to wild, and you installed the third largest one.
For street, today, we still only have about 4 sizes , given that a size is 7 or 8 degrees, from 262 down the list to 284. If you include the 292 which IMO, in a SBM, is not really all that streetable, it comes to 5 sizes; and looks something like;
262, 268, 276, 284,
and 292