E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Doncaster.
Sigebert, monk of Gemblours, in 1100, derived this word from Thong-ceaster, the Castle of the thong, and says that Hengist and Horsa purchased of the British king as much land as he could encompass with a leather thong. The thong was cut into strips, and encompassed the land occupied by the city of Doncaster.
1
This is the old tale of Dido and the hide, and so is the Russian Yakutsks. (See BURSA.)
2
Of course it means the City on the river Don. (Celtic, Don, that which spreads.)