It is thought that it comes from the Tibetan monks that originally began development of the breed (along with Lhasa Apso). Shih-tzu means Lion. Here is the breed parent club which often has the history and a ton of other breed information so you can get more details.
http://americanshihtzuclub.org/breed_astc_history
www.dogfoodanalysis.com
http://americanshihtzuclub.org/breed_astc_history
www.dogfoodanalysis.com