Kretek is an Indonesian word for clove cigarettes derived from the crackling sound made when burned: "keretek-keretek". They are mixed with tobacco and other flavorings, and if paper's not available, cornhusks are utilized. More significantly, clove-- a sweet, pungent spice sometimes used on hams-- is indigenously grown on the Indonesian islands of Molucca.
Many of the clove groves on Molucca came from a tradition of planting a tree for every child born, and the spice became so important in the spice trades, the Dutch burned up excess plants to lower supply and thus increase prices, causing a riot.
Most kretek cigarettes (especially the Kretek brand) are roughly forty percent clove, with the remaining ratio containing nicotine containing tobacco and various colorings and flavorings (chocolate, vanilla, etc.) The Kretek company sells djarum cigarettes as well, along with other exotic styles, i.e. Bali Hai, etc.