Where does “neamhréasúnach” come from?

neamhréasúnach (Irish) comes from Irish réasúnach, 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.

neamhréasúnach (Irish): irrational, unreasoning; unreasonable, excessive

Definitions

irrational, unreasoning; unreasonable, excessive

Ancestry of “neamhréasúnach”, step by step

Step	Language	Word	Meaning
1	Irish	réasúnach	reasoning, rational; Synonym of réasúnta
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- →