Where does “tiomsaitheoir” come from?

tiomsaitheoir (Irish) comes from Irish -itheoir, from Irish -óir, from Old Irish -óir, from Proto-Brythonic -ọr, from Latin -ārius, from Proto-Italic *-āzios — Forms relational adjectives to nouns (and rarely numerals).

tiomsaitheoir (Irish): gatherer, collector; collector; compiler

Definitions

gatherer, collector; collector; compiler

Ancestry of “tiomsaitheoir”, step by step

Step	Language	Word	Meaning
1	Irish	-itheoir	used after verbs ending in
2	Irish	-óir	-er; suffix appended to words to create an agent...
3	Old Irish	-óir	er, -or
4	Proto-Brythonic	-ọr	—
5	Latin	-ārius	er
6	Proto-Italic	*-āzios	Forms relational adjectives to nouns (and rarely numerals)

Every word from Proto-Italic *-āzios →Every word from Latin -ārius →Every word from Irish -óir →