Starting in the Middle Ages, a squire was the shield- or armour-bearer of a knight. At times, squires acted as a knight's errand runner. Use of the term evolved over time. Initially, squires were a knight's apprentices. Later, a village leader or a lord of the manor might be called a squire, and still later, the term applied to key public figures, such as justices of the peace or members of parliament. In contemporary American usage, squire is the title given to justices of the peace or similar local dignitaries.
Squire is a shortened version of the word esquire, from the Old French escuier (modern French écuyer), itself derived from the Late Latin scutarius ("shield bearer"), in medieval or Old English a scutifer. The Classical Latin equivalent was armiger, "arms bearer".
The most common definition of squire refers to the Middle Ages. A squire was typically a teenaged boy, training to become a knight. A boy became a squire at the age of 14. Squires were the second step to becoming a knight, after having served as a page. Boys served a knight as an attendant or shield carrier, doing simple but important tasks such as saddling a horse or caring for the knight's weapons and armour. The squire would sometimes carry the knight's flag into battle with his master.
A knight typically took his squire into battle and gave him a chance to prove himself. If he proved his loyalty and skill in battle, he would have a "dubbing", an official ceremony that made him a knight. However, during the Middle Ages, the squire's rank came to be recognized in its own right; it was no longer assumed that a squire would automatically become a knight. The connection between a squire and any particular knight also ended, as did any shield-carrying duties.