I really like this name! And to clarify on pronunciation, it is pronounced "Shown", as in the phrase "the film was shown on TV". So, not "Sean", not "Shorn", not "See-on", but "Shown" (with a long "o").
The person above is incorrect. It's not pronounced "shown" It's pronounced just like Sean, Shaun, Shawn etc. I can guarantee I'm correct, I'm Welsh and I have a cousin called Sion, and I know countless Sions and they all pronounce it just like Sean.
Met someone called this, and they pronounced it 'Sean'. I called him Sion though as I had no idea, and of course he laughed. It's such an unusual name these days!
I have only encountered this name once, in historical records from the 1810s. I had no clue how to pronounce it or where it came from. I think it's kind of strange. Certainly not mainstream (at least not in the USA).
Corn here is pronounced like the word "con" but add the r. (If that makes sense)?