Several alternatives, as shown here:
http://en.wiktionary.org/wiki/deoch_an_dorais#Scottish_Gaelic

I'm not a Gaelic speaker, but did wrestle with it trying to learn it for a while, and it's true that there are regional variations in different parts of Scottish Gaeldom.

And yes, there are quite a lot of words used in/by Scots which have a Gaelic origin (tho' the person speaking may not know it!), just as you'll hear Gaelic speakers throw in "English" or Scots words when there is no original Gaelic word for what they are saying. (As the French talk about le weekend!)