Aber doch, a question for the Gaelic speakers

Factual Questions
1

I have come to the conclusion that both aber and inver (as in Aberdeen, Aberystwyth (although not Gaelic), Inverness, Invergarry and other place names) has something to with locations in respect to rivers, but what do they actually mean?

2

From MacBain’s Etymological Dictionary of Scottish Gaelic:

abar or obair (both obsolete): confluence (NB aber is listed as the Welsh translation of this word)
inbhir: a confluence of waters