In the Roman and Byzantine Empires of the 5th and 6th centuries AD, the comes stabuli (count of the stable) was the person in charge of the stables at the imperial court.
The Franks borrowed the title and but changed the position slightly to the head of the royal stud. During the 12th century in France, the comes stabuli became an important commander in the army and the title became conestable in Old French.
Eventually the word was borrowed into English as constable and referred to “an officer of the peace” - this meaning was first recording in 1596. During the 19th century, a regular police force was established in England and the police officers were given the title constable under a chief constable.
Today constable is the lowest rank in the British police, followed by sargeant, while Chief Constable is the highest rank.