I posted mention of uillean in Grove, 1906, but, not having that book of that date available, I don't know who wrote the reference.

Oxford English Dictionary:
Union pipes- "A form of bagpipes in which the wind-bag is inflated by bellows worked by the elbow." OED. From piob uilleann, piob = pipe plus genitive singular of uille (= elbow).
The word uillean was admitted to the OED in the 1987 Supplement.

Now lets not have any argument with the authority! (He, he, he!)