E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
from the Greek sukophants, fig-blabbers. The men of Athens passed a law forbidding the exportation of figs; the law was little more than a dead letter, but there were always found mean fellows who, for their own private ends, impeached those who violated it; hence sycophant came to signify first a government toady, and then a toady generally.
I here use sycophant in its original sense, as a wretch who flatters the prevailing party by informing against his neighbours, under pretence that they are exporters of prohibited figs.Coleridge: Biography, vol. iii. chap. x. p. 286.