My Japanese dictionary is also not helpful. No result for this. One thing I come up with is a phrase in my dialect around the Kansai region. "い(ー)やや、こやや" is used among small kids when they notice that someone else did a bad thing. They make fun of him/her, singing this. いやや in my dialect means like "I don't like it=いやです in the polite and standard expression". The こやや part does not have a specific meaning. It seems to be something like a shout in the phrase, using a similar sound to いやや. This phrase often includes; い（ー）やや、こやや、せんせいにゆうたろ[this part is also a dialect=せんせいに言うぞ=I'm/We're gonna tell our teacher] FYI, see 大阪府 in http://ameblo.jp/sekihideo/entry-10229300130.html I said this a lot when I was little.