All u 80's guys that know cams????
It's a term that was already dated by the 80s. It dates back to flathead Ford days (before my time) when you had a "Full Race cam" and "3/4 race cam". Probably more closely resembles the term "street/strip" today, although the specs are probably quite different.
If your dad had a "purpleshaft cam" it was from Direct Connection (now Mopar Performance) and was probably the "hemi grind" or the .509, as they were called.