E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Eckhardt.
A faithful Eckhardt, who warneth everyone (German). Eckhardt, in German legends, appears on the evening of Maundy Thursday to warn all persons to go home, that they may not be injured by the headless bodies and two-legged horses which traverse the streets on that night.