noun, noun or participle which takes 'suru'
farting while asleep
Colloquial term for passing gas during sleep. Often used humorously or in casual conversation.
昨夜、寝っ屁をしてしまったらしい。
It seems I farted in my sleep last night.
彼はよく寝っ屁をする。
He often farts while asleep.
Compound of 寝 (ne, 'sleep') and 屁 (he, 'fart'), with the colloquial gemination っ and rendaku voicing. The exact historical derivation is uncertain, but it is a straightforward colloquial formation.