dock 2 
(dŏk)
(dŏk)n.
1. The solid or fleshy part of an animal's tail.
2. The tail of an animal after it has been bobbed or clipped.
tr.v. docked, dock·ing, docks
1. To clip short or cut off (an animal's tail, for example).
2. To deprive of a benefit or a part of one's wages, especially as a punishment: The company docks its employees for unauthorized absences.
3. To withhold or deduct a part from (one's salary or wages).
[Middle English dok.]