Early 19th century. From French rancio wine having a distinctive rich flavour or bouquet, redolent of nuts, butter, or overripe fruit, produced by oxidation or maderization, characteristic flavour of such a wine, quality of possessing these characteristics and its etymon Spanish rancio (noun) characteristic flavour of an overripe wine, quality of possessing these characteristics, wine having a distinctive rich flavour or bouquet, redolent of nuts, butter, or overripe fruit, produced by oxidation or maderization (although this is apparently first attested later: 1809 or earlier), (adjective) (of wine) becoming more delicious and mellow with age, specifically sense developments of rancio (adjective) rancid, (noun) rancidity from classical Latin rancidus.