E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Shakespeare calls it the baleful mistletoe (Titus Andronicus, ii. 3), in allusion to the Scandinavian story that it was with an arrow made of mistletoe that Balder was slain. (See KISSING UNDER THE MISTLETOE.)
The word mistletoe is a corruption of mistel-ta, where mist is the German for dung, or rather the droppings of a bird, from the notion that the plant was so propagated, especially by the missel-thrush. Ta is for tan, Old Norse tein, meaning a plant or shoot.