This is not an Arabic word: it is the name of a language spoken in eastern Africa.
Swahili used to be written in Arabic script (much as Ottoman Turkish and Bosnian were whereas as modern Turkish and Bosnian are now in latin script) as many speakers of the language (even today) are of the Islamic faith and the language also incorporated many words of Arabic origin, however the languages are not of the same origin. Arabic is a semetic language (related to Hebrew and Aramaic) and Swahili is related to southern African languages.

I find your question slightly strange but I hope this helps!

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Note added at 3 hrs 39 mins (2004-03-12 16:11:02 GMT)
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A couple of addenda:
I checked it up in my 1980s copy of the OED. Swahili is as armaat and Colin state it to be in origin (i.e. Arabic)and its Arabic meaning. The word entered the English language in 1814, but today it means (and has always meant) in English the name of this language (and more loosely, people). It is actually a major East African language and is no longer only spoken by \"coastal\" people. It is indeed a lingua franca for many.

Apparently, the language is still written in Arabic script by some but can also be written in Latin script (as it is in taught at the university I attended).