reasonablereasonable

Reasonable comes from Middle English resonable, from Old French resnable ‘wise’, from Latin ratiōnābilis ‘rational’, from ratiō ‘reason’, from reor ‘to reckon’.

1. Latinc. 75 BCE–200 CEreor¹‘to reckon, think’
2. Latinc. 75 BCE–200 CEratiō²‘reason’
3. Latinc. 75 BCE–200 CEratiōnābilis²‘rational’
4. Old Frenchc. 842–1400resnable²‘wise’
5. Middle Englishc. 1150–1500resonable²
6. Englishearliest quotation 1634reasonable²

1. ¹ Wiktionary, Latin ratio
2. ² Wiktionary, English reasonable
3. Earliest quotation in Wiktionary’s entry: 1634, William Wood, Beasts Living in the Water: “The wiſdome and underſtanding of this Beaſt [the beaver],…”.