Comparative evidence

neu̯

• Lat. adnuō -ere ‘to nod’, ‘grant’, ‘concede’, ‘approve’ (OLD: 51)

• Lat. abnuō -ere ‘to move the head (or eyes) upwards or away in token of refusal’ ‘shake one’s head’, ‘say no’, ‘refuse’, ‘decline’  (OLD: 8)

References

OLD = Glare, P. G. W. 1968. Oxford Latin Dictionary. Oxford: Clarendon Press.