A pet peeve of mine since I got back to Texas is that people call the pronunciation of Spanish by Spaniards a "lisp." You may or may not know this, but is Spain the correct pronunciation of the letter "z" and the soft "c" is a voiceless "th" sound like in "theater." Because Americans are used to hearing South American Spanish, which pronounces the "z," the soft "c," with the "s" sound, when they hear a Spaniard (or someone like me, who speaks Spanish with the Spaniard accent) it sounds to them as if they were lisping, and they call it so accordingly.
Then, you get this story about how one Spanish king had a lisp. So to make him feel better, all of the people around him began to speak as he did. And there you have it=why Spaniards lisp. This is all complete crapola.
Okay people. A lisp is a speech defect. It means that the person speaking with a lisp is not pronouncing words correctly. Like they are defective in some way.
This is the real story. The "th" sound was evident in Spain even before the Spanish travelled to the New World. The sound developed from the sounds associated with the cedilla (ç) and the "z." So the original pronunciation of the "z" and the soft "c" is as a voiceless "th."
However, in some areas of Andalucia they started pronouncing them as an "s." One of the articles that I read says that this might have been because of the strong the Mozarabic influence in the south. People from Seville and other places in Andalucia still speak like this today (some also still use "ustedes" instead of "vosotros" which is another difference in the use of the language).
Well, I bet most of you didn't know this, but many of the famous explorers and "conquistadores" from Spain were from Andalucia. As were many of the subsequent Spaniards that immigrated to the New World. They were the original "mispronouncers" of the the "z" and the soft "c." They removed themselves from their original population and the "sss" stuck.
So if we are to say that someone is mispronouncing, who would it be? I, for one, would have to say that no one is mispronouncing. I believe that language is alive and it evolves as cultures evolve. I also speak American English, which is different than British English. If I say that the British have a speech impediment because when they pronounce the "r" they open their mouths more, that would be stupid.
So please, stop saying that Spaniards have a lisp. It's insulting.