What is "by the rood"

Rood \Rood\ (r[=oo]d), n. [AS. r[=o]d a cross; akin to OS. r[=o]da, D. roede rod, G. ruthe, rute, OHG. ruota. Cf. Rod a measure.]

1. A representation in sculpture or in painting of the cross with Christ hanging on it.

   Note: Generally, the Trinity is represented, the Father as an elderly man fully clothed, with a nimbus around his head, and holding the cross on which the Son is represented as crucified, the Holy Spirit descending in the form of a dove near the Son's head. Figures of the Virgin Mary and of St. John are often placed near the principal figures.

   Savior, in thine image seen Bleeding on that precious rood.
   --Wordsworth.

2. A measure of five and a half yards in length; a rod; a perch; a pole. [Prov. Eng.]

3. The fourth part of an acre, or forty square rods.

   By the rood, by the cross; -- a phrase formerly used in swearing. ``No, by the rood, not so.''
   --Shak.

   Rood beam (Arch.), a beam across the chancel of a church, supporting the rood.

   Rood loft (Arch.), a loft or gallery, in a church, on which the rood and its appendages were set up to view.
   --Gwilt.

   Rood screen (Arch.), a screen, between the choir and the body of the church, over which the rood was placed.
   --Fairholt.

   Rood tower (Arch.), a tower at the intersection of the nave and transept of a church; -- when crowned with a spire it was called also rood steeple.
   --Weale.

   Rood tree, the cross. [Obs.] ``Died upon the rood tree.''
   --Gower.

adv. (non-gloss definition: Used as an oath to emphasis the veracity of an associated statement.)