I just came across this great little quote from Bruce Gordon’s book, “Calvin:”

. . . Terms like ‘Calvinist’ and ‘Zwinglian’ were not badges worn with pride so much as insults used by opponents to indicate that the people were not Christians.” (p. 185)

The time frame this is referring to, is at least Calvin’s life time.

I suppose this is true today, as well; it all depends on what direction your looking at it from.