The answer to this is not as easy as you may have expected. The country has been called Cambodia since 1990, before that Peoples Republic of Kampuchea (1976 - 1990) Cambodia (1975 - 1976) Khmer Republic (1970 - 1975) prior to that it was Cambodia and at various stages in history has had various other names that include Funan, Chenla, Khmer and Kampochea. Maybe some scholar can provide dates and name changes for all time previous.
Previously known as Kampuchea but also as Cambodia - the official name changing between the two over the years. Pre 1953 it was part of French IndoChina and was originally part of the Khmer Empire.