CASSIVELAUNUS, or Cassivellaunus, a British chieftain, ruler of the country north of the Thames, who led the native tribes against Julius Caesar on his second expedition (54 b.c.) (see Britain). After several indecisive engagements, Caesar took the camp of Cassivelaunus, who was obliged to make peace on condition of paying tribute and giving hostages. But these promises were not meant to be kept, and it appears certain that the tribute was never paid. According to Bede (Hist. Eccles. i. 2), the remains of Cassivelaunus's entrenchment were visible seven or eight centuries later.
See Caesar, B.G. v. 11-22; Dio Cassius xl. 2, 3; Orosius vi. 9. 6; Eutropius vi. 17; Polyaenus, Strategemata, viii. 23. For the etymology of the name (which is Celtic in origin, and appears later as Caswallon) see J. Rhys, Celtic Britain, pp. 289-290 (1904); C.I. Elton, Origins of English History (1890); and Stock's edition of Caesar, De Bella Gallico(1898).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)