What could be more Australian than the droning sound of this native instrument? Yet there's a linguistic mystery about it. Firstly, the name isn't recorded in Australian English until 1919, astonishingly late. And it isn't Aboriginal - native names include "yidali", "illpera" and "bombo", but nothing that sounds even vaguely like "didgeridoo". Lexicographers have traditionally got round this by saying it is imitative, but "didgeridoo" bears scant relation to the noise the instrument makes. Now Dymphna Lonergan, currently working on a PhD thesis about the Irish influence on Australian English, may have solved the problem. Her theory appeared in Australian newspapers six months ago, and is reported in more detail in the current issue of Ozwords, published by the Australian National Dictionary Centre. She points to a possible Irish source in two words "dúdaire" and "dubh". Gaelic spelling is in a class by itself: the words are actually said rather like "doodjerreh" and "doo". The first means "trumpeter"; the second means "black". Put them together (adjective following noun in Gaelic) and you get a phrase that means "black trumpeter" and which sounds remarkably like the instrument's name.
Michael Quinion has a website called World Wide Words. You can check it out at http://www.worldwidewords.org