The inspiration for Shrek ‘allegedly’ was the famous wrestler Maurice Tillet. Born in 1903 in The Urals in Russia, to a French family, which in 1917, due to the Revolution, returned to France. Tillet was a wrestler and a very intelligent person. He was a poet and writer who could speak 14 languages.

I couldn't verify this with DreamWorks but it seems to be accepted information with most movie information sites I found.