The "woolen" pipes appear in the Merchant of Venice. No one knows what they were.
Seamus Ennis, in a tape put out by green Linnet in 1977, says that he plays on pipes made 150 years ago by Coyne in Dublin.

I guess that the argument about Union pipes will continue. The Oxford English Dictionary passes, saying "The etymological relationship between the two terms [uillean and union] is uncertain." They go on to say that uillean is now predominant.
The earliest publication in English of the term uillean seems to be in Grove's Dictionary of Music, 1906. Anyone with verifiable earlier examples?