tonne

Etymology

From French tonne (“metric ton”). Doublet of ton and tun.

noun

1. (chiefly UK) Synonym of metric ton, a unit of mass equal to 1000 kg.
   Although loads of up to 900 tonnes could be handled by one of these locomotives, in practice the load is limited to 790 tonnes by drawgear. 1961 February, “Letters to the Editor: Swiss railways”, in Trains Illustrated, page 126
   The metric ton or 'tonne' is accepted as a synonym for the megagramme, and this form Is to be preferred on the grounds of brevity and familiarity in the industry. It may be as well to use the pronunciation 'tunnie' until the risk of confusion with the old ton has passed. 1971, Transactions of the Royal Institute of Naval Arcihtects, volume 113, page 215
   The British Steel Corporation, going metric but realising the possible confusion between a ton and a tonne (1,000 kilograms) has directed its staff to pronounce ‘tonne’ ‘tunnie’. 1972 May, Which
   The tonne rhymes with con (perhaps not in North America!) to distinguish it from the non-SI unit of weight, the ton rhyming with bun. 2002, Richard Chapman, Physics for Geologists, CRC Press, published 2002, page 138