In 1840 there was a Polish explorer called Paul Strzelecki who named the mountain after a Polish freedom fighter called General Tadeusz Kosciuszko whose tomb is of a similar shape back in Krakow.
Before 1997 the name was spelled Kosciusko without the ‘z’. The Geographical Names Board of New South Wales agreed to change the spelling to ‘Kosciuszko’ which is the correct spelling of the General Surname.