I am unsure what やついておる means in the following sentence:

> …貴様、何をにやついておるのだ…？

For some context Person A is comforting Person B who has just heard some happy
news and gotten emotional. Person C says the above sentence.

I've not come across やついておる in my studies before, can someone explain this to
me?
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2017-03-07T16:42:17.543
44165
2017-03-07T18:24:02.417
20179
question
meaning sentence
What does やついておる mean?
I think you parsed it wrong.

> 貴様、何を **にやついておる** のだ…？  
>  _What are you grinning at, you bastard?_

It's [にやつく](http://www.excite.co.jp/world/j_dictionary/ITEM-
DJR_niyatuku_-010/%E3%81%AB%E3%82%84%E3%81%A4%E3%83%BB%E3%81%8F/?itemid=DJR_niyatuku_-010&title=%E3%81%AB%E3%82%84%E3%81%A4%E3%83%BB%E3%81%8F)
'smirk; grin', a compound formed from the sound symbolic noun にや 'smirk; grin'
along with the verb つく.

You can tell it's not 何を＋に because that sequence of particles doesn't go
together.
CC BY-SA 3.0
2017-03-07T18:24:02.417
44166
2017-03-07T18:24:02.417
44165
answer