Where does “tar-iadhadh” come from?

tar-iadhadh (Scottish Gaelic) comes from Scottish Gaelic tar-, from Old Irish tar, from Old Irish a, from Proto-Celtic *ā, from Proto-Indo-European ō — oh, ah.

tar-iadhadh (Scottish Gaelic): overlap

Definitions

overlap

Ancestry of “tar-iadhadh”, step by step

Step	Language	Word	Meaning
1	Scottish Gaelic	tar-	trans-, over-
2	Old Irish	tar	over, across
3	Old Irish	a	nominative/accusative singular neuter of in; that...
4	Proto-Celtic	*ā	O (vocative particle)
5	Proto-Indo-European	ō	oh, ah

Every word from Proto-Indo-European ō →Every word from Proto-Celtic *ā →Every word from Old Irish a →