Where does “preabadh” come from?

preabadh (Irish) comes from Irish -adh, from Old Irish -ad, from Proto-Celtic -tus, from Proto-Indo-European -tus — Derives action nouns from verb roots.

Ancestry of “preabadh”, step by step

Step	Language	Word	Meaning
1	Irish	-adh	Creates the regular verbal noun of...
2	Old Irish	-ad	suffix forming verbal nouns; suffix forming the...
3	Proto-Celtic	-tus	Forms action nouns from verb stems
4	Proto-Indo-European	-tus	Derives action nouns from verb roots

Every word from Proto-Indo-European -tus →Every word from Irish -adh →Every word from Old Irish -ad →