The current disaster in Japan raises the question of the origin of the word tsunami. It is from Japanese 津波, where 波 [nami] is "wave" and 津 [tsu] here means "harbor". It was apparently first used in English in 1897 by Lafcadio Hearn in his Gleanings from Buddha Fields. The Japanese Wikipedia article contains a discussion of early English usage.
In English the word is pronounced [sunami] rather than [tsunami] since English does not allow syllable-initial [ts]. This is yet another example of insane English spelling practices and of the fact that they cannot be blamed entirely on the preservation of archaic spellings. The word could perfectly well have been borrowed into English as sunami. The person learning to write English must memorize the fact that this [s] is written <ts> for no reason at all. Note that the English spelling does not even have the virtue, whatever that might be, of preserving the Japanese spelling since Japanese is not written in Roman letters.