exorcism
儺 centers on ritual exorcism: a person performing a ceremony to drive away evil spirits.
儺 combines 亻 (person) with 難, which likely contributes the sound and may relate to difficulty or affliction, suggesting a person dealing with spiritual trouble through exorcism.
A person 亻 performing a difficult 難 ritual to drive out evil: that is exorcism.
For ナ, picture a shaman shouting 'Nah!' to banish a spirit: Nah -> ナ, and the person 亻 drives the difficult 難 presence away.