I think much credit for plethora's popularity should definitely go to the movie "The Three Amigos". Read:
Jefe: I have put many beautiful piñatas in the storeroom, each of them filled with little surprises! El Guapo: Many piñatas? Jefe: Oh yes, many! El Guapo: Would you say I have a plethora of piñatas? Jefe: A what? El Guapo: A plethora. Jefe: ...Oh yes. You have a plethora. El Guapo: Jefe, what is a plethora? Jefe: Why, El Guapo? El Guapo: Well, you told me I have a plethora. And I just would like to know if you know what a plethora is. I would not like to think that a person would tell someone he has a plethora, and then find out that that person has no idea what it means to have a plethora! Jefe: Forgive me, El Guapo, I know that I, Jefe, do not have your superior intellect and education, but could it be that once again, you are angry at something else, and are looking to take it out on me?