Merriam-Webster Collegiate Dictionary - companion

 I. noun  Usage: often attributive  Etymology: Middle English compainoun, from Anglo-French cumpaing, cumpaignun, from Late Latin ~-, companio, from Latin com- + panis bread, food — more at food  Date: 13th century  1. one that accompanies another ; comrade, associate; also one that keeps company with another  2. obsolete rascal  3.  a. one that is closely connected with something similar  b. one employed to live with and serve another  4. a celestial body that appears close to another but that may or may not be associated with it in space  II. verb  Date: 1622  transitive verb accompany  intransitive verb to keep company  III. noun  Etymology: by folk etymology from Dutch kampanje poop deck  Date: 1762  1. a hood covering at the top of a ~way  2. ~way