What ever happened to the term "brassiere"? This was the only term used to describe this particular garment in my youth but seems to have been replaced (entirely?) by the shortened form "bra." How did that happen? And were we looking at the time?

"Bra" seems to have enlarged in its meaning, at the same time. The rock-protection cover placed on the front ends of some sports cars is called a bra, I think.