Stock Exchange term for a percentage paid by a seller of stock for the privilege of keeping back or delaying its delivery till the following account or to any other future day agreed upon.
1850 Keyser Law Stock Exch., The term Backwardation is employed when stock is more in demand than money, and a premium is given to obtain the loan of stock against its value in money. a1860 C. Fenn Eng. & For. Funds (1883) 127 Backwardation is paid by the speculator for the fall, or the Bear, in order to postpone delivery until the following account. 1880 Society 3 Sept. 16 The Bear a good contango loves, The Bull a backwardation. {OED}

contango? [there's one for teD]
The percentage which a buyer of stock pays to the seller to postpone transfer to the next or any future settling day; continuation; the opposite of backwardation.