The bailiff is an officer of the court responsible for keeping order and maintaining appropriate courtroom decorum and has custody of the jury.
A bailiff was an estate manager for the lord of the manor in feudal England, beginning in the 11th century. Towards the end of the Middle Ages, the bailiff's duties shifted to become an assistant the sheriff, because lords were often renting their manors to farmers and did not need estate managers anymore. Then farmers and landlords used bailiffs as rent collectors.
The office or jurisdiction of a bailiff was known as his "bailiwick" (BAY-lih-wik).
In modern America bailiffs are messengers and ushers in the court system. Today a "bailiwick" can mean any person's special domain, as in "that question about the party can be best answered by Susan, because managing the party is in in her bailiwick."