1950s- First aftermarket "racing wheels" made of magnesium alloy. The California car culture coins the term "Mag Wheel" to describe them.

1960s- aluminum copies of the racing wheels started showing up along with less expensive aluminum racing wheels. Most still called them all "Mags"

1970s- many types and styles of aluminum wheels started showing up both as OEM and aftermarket The term "mag" was still often used to describe the wheels. Just like the term "English Racer" was used to describe lightweight bikes with hand brakes...

Often the aftermarket aluminum wheels were called by their names, i.e. "he has Cragers", or "ETs". Probably around this time the term "alloy" started creeping in to more common usage.

Now days the hip people call them "rims"