What does "aber" mean?

A hamlet in Llanwenog community, Ceredigion, Wales (OS grid ref SN4748).

Aber

/ˈæbɚ/ name

name ·Rare ·Advanced level

Proper Noun

1
A hamlet in Llanwenog community, Ceredigion, Wales (OS grid ref SN4748).
2
A hamlet in Talybont-on-Usk community, Powys, Wales (OS grid ref SO1021).
3
A railway station in Caerphilly, Caerphilly borough, Wales (OS grid ref ST1486).
4
Clipping of Aberystwyth. abbreviation, alt-of, clipping
5
Clipping of Abergwyngregyn, used by the former Aber railway station (Gwynedd). abbreviation, alt-of, clipping

From Welsh aber (“river mouth, confluence”).