reason
‘the basis or motive for an action, a decision, or a conviction; a declaration made to explain or justify an action, a decision, or a conviction’
Lexical development traced from the Tamil root:
E. reasoune, reeson, resone < A.F. resoun < O.F. raison ‘course; matter; subject; language, speech; thought, opinion’ < Lat. rationem ‘a reckoning, account, a numbering, calculation’ < ratus < reri ‘to reckon, think’ < ree < re- < Tamil ār