E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Sir John Maundeville, speaking of the Pool of Siloe, says, Fast by is the elder-tree on which Judas hanged himself when he sold and betrayed our Lord. Shakespeare, in Loves Labours Lost, v. 2, says, Judas was hanged on an elder. (See FIG-TREE.)