Where does “réasúnaíocht” come from?

réasúnaíocht (Irish) comes from Irish réasúnaigh, from Irish réasún, from Middle Irish résún, from Anglo-Norman raisun, from Old French reson, from Latin ratiō, from Latin -tiō, from Latin dissertātiō — small stone, pebble; gravel, rubble.

réasúnaíocht (Irish): reasoning; rationality; rationale

Definitions

reasoning; rationality; rationale

Ancestry of “réasúnaíocht”, step by step

Step	Language	Word	Meaning
1	Irish	réasúnaigh	to reason, rationalize
2	Irish	réasún	reason, reasoning faculty; reasonableness, sense;...
3	Middle Irish	résún	reason
4	Anglo-Norman	raisun	Alternative form of reson
5	Old French	reson	logic, logical reasoning
6	Latin	ratiō	reason, reasoning, explanation, ground, motive, rationality, rationale, purpose
7	Latin	-tiō	tion, -ation, -ing
8	Latin	dissertātiō	(spoken) dissertation, discourse, disquisition
9	Latin	dissertus	arranged, disposed; explained
10	Latin	disserere	second-person singular future passive indicative...
11	Latin	dis-	asunder, apart, in two; reversal, removal;...
12	Latin	calceus	shoe
13	Latin	calx	limestone; chalk; the finish line
14	Ancient Greek	χάλιξ	small stone, pebble; gravel, rubble

Every word from Ancient Greek χάλιξ →Every word from Latin -tiō →Every word from Latin dis- →