From ayọ̀ ("joy") + dé ("arrive") + ilé ("home"): "joy has come home." Shortened to Ayo or Dele.
Source: Yoruba oríkì surname, cross-referenced across the DiscoverYorùbá surnames guide and the -dé ilé "come home" pattern attested in 0043 (Adéwálé, Ọláwálé)