What is "arm in arm"

Arm \Arm\, n. [AS. arm, earm; akin to OHG. aram, G., D., Dan., & Sw. arm, Icel. armr, Goth. arms, L. armus arm, shoulder, and prob. to Gr. ? joining, joint, shoulder, fr. the root ? to join, to fit together; cf. Slav. rame. ?. See Art, Article.]

1. The limb of the human body which extends from the shoulder to the hand; also, the corresponding limb of a monkey.

2. Anything resembling an arm; as,

   1. The fore limb of an animal, as of a bear.

   2. A limb, or locomotive or prehensile organ, of an invertebrate animal.

   3. A branch of a tree.

   4. A slender part of an instrument or machine, projecting from a trunk, axis, or fulcrum; as, the arm of a steelyard.

   5. (Naut) The end of a yard; also, the part of an anchor which ends in the fluke.

   6. An inlet of water from the sea.

   7. A support for the elbow, at the side of a chair, the end of a sofa, etc.

3. Fig.: Power; might; strength; support; as, the secular arm; the arm of the law.

   To whom is the arm of the Lord revealed?
   --Isa. lii. 1.

   Arm's end, the end of the arm; a good distance off.
   --Dryden.

   Arm's length, the length of the arm.

   Arm's reach, reach of the arm; the distance the arm can reach.

   To go (or walk) arm in arm, to go with the arm or hand of one linked in the arm of another. ``When arm in armwe went along.''
   --Tennyson.

   To keep at arm's length, to keep at a distance (literally or figuratively); not to allow to come into close contact or familiar intercourse.

   To work at arm's length, to work disadvantageously.

adv. 1 with arms linked together 2 (context figuratively English) in collusion with, in concert with alt. 1 with arms linked together 2 (context figuratively English) in collusion with, in concert with