Thaddeus von Clegg was an immigrant (to the USA) German clockmaster who constructed the first kazoo in the 1840s.
The kazoo, also called Clegghorn, is based on the African mirliton, and was a popular African-American folk instrument during the 19th century. The manufactured version we know today was invented in Macon, Georgia, by an African American named Alabama Vest, in the 1840s. The first manufactured kazoo was made by Thaddeus Von Clegg, a German clockmaker in Georgia, and the instrument was introduced to the South at the Georgia State Fair in 1852.