The affix vuñ comes after the verbs devi 'to lament' and kruśa 'to cry' when an upasarga is in composition with them.,
As आदेवकः 'one who sports or laments'; आक्रोशकः 'vociferous, a reviler'; परिदेवकः 'one who laments'; परिक्रोशकः 'a reviler'.
Why do we say 'when in composition with an upasarga'? Observe देवयिता and क्रोष्ठा formed by तृन् 3.2.135.,