ton: [14] Ton originated as a variant of tun ‘barrel’ [OE]. At first it was used for a unit of capacity, equal to the space occupied by a tun of wine, but by the end of the 15th century we find it being applied to a unit of weight. Tun itself was acquired from medieval Latin tunna, which was probably of Gaulish origin. Another of its descendants was Old French tonne, whose diminutive tonel was borrowed into English as tunnel [15]. This was originally used for a ‘tubular net for catching birds’, and then for a ‘chimney flue’ or ‘funnel’. It was not applied to an ‘underground passage’ until as recently as the late 18th century. => tun, tunnel
