Originally Posted by mafoofan
My understanding is that "Donegal" refers to tweed spun in the Irish region of that name, but since the plain-woven flecked pattern has become so iconic, it has become known as "Donegal" regardless of where it's from. The flecks are from the way the yarn itself is processed, so they can appear in weaves other than plain.
I think this is basically correct. I also think Donegal tweed, like Harris, originally referred to handwoven cloth, although, unlike Harris, Irish mills like Magee now offer machine woven cloth as Donegal as well. In addition,the name "Donegal" is not protected in the same manner as Harris and, therefore, cloth can be sold as Donegal by anybody regardless of place of origin, method of weaving or pattern.
I think some of the confusion comes from the fact that donegal (with a lower case "d") has come to be used as a generic term for a woollen tweed with those characteristic flecks in it and you othen see such tweed offered by some merchants as "donegal style" fabric.