!Kung is a language spoken by Kalahari bushmen and one sound of the language is a click represented by the exclamation point. The click is a tongue-roof of the mouth click, like you do when you make the tick-tock sound of a clock. It's a very strange language. If you've ever seen the movie The Gods Must Be Crazy, the language the bushman speaks is !Kung, or some similar language.
'Bushmen' is a South African name for the San people, also known as Khoi-San, an ethnic group of the Kalahari Desert in Botswana and Namibia. The San language uses click sounds.
Click Song a South African folk song popularized by singer Miriam Makeba, who owes her introduction to the general public to Belafonte, Harry. The 'click' referred to is a sound in the language of the Xhosa people, a tribe of the Zulus, and done by snapping the tongue away from the roof of the mouth. It's represented in English by 'xh' or '!x', so the the tribal name, for instance, would be pronounced, more or less, 'ossa'. [cgrg.ohio-state.edu/%7Espencer/FF/C.html]