òpònú noun /ò.k͡pò.nṹ/
Definitions
  1. idiot, daft person offensive
Etymology
From ò- (“nominalizing prefix”) + ponú (“to be daft”).
Component words
ò-nominalizing prefixponúto be daft
Source: Wiktionary, where this word is spelled “oponu”. Reference: en-oponu-yo-noun-wGAM3lFm