1530s, "corner, angle," from French canton "angle, corner (of a room); piece, portion of a country" (13c.), from Italian (Lombard dialect) cantone "region," especially in the mountains, augmentative of Latin canto "section of a country," literally "corner" (see cant (n.2)).
From 1570s as a term in heraldry and flag descriptions. From c. 1600 as "a subdivision of a country;" applied to the sovereign states of the Swiss republic from 1610s.
18c., the former English transliteration of the name of the major port city in southern China and the region around it, properly the name of the region, now known in English as Guangdong (formerly also transliterated as Quang-tung, Kwangtung), from guang "wide, large, vast" + dong "east." The city name itself is now transliterated as Guangzhou (guang, from the province name, + zhou "region"). One of the first Chinese cities open to Westerners; the older form of the name is from the British-run, Hong Kong-based Chinese postal system.