How come the last name Smith is so common?
In Late Medieval Europe, second names became a popular aspect of society due to increasing populations calling for people to need the ability to identify which person was which. For example, in Early Medieval Europe most people lived in small villages where there would only be one or two people with a particular name, and so surnames were not needed. In the larger and more populous towns and cities of the late medieval period, however, surnames were needed to distinguish between the numerous different people within a town with the same name.
In these cities, one of the most common occupations for an individual would be a black smith, so these people along with all of their families would gain the surname Smith. Eventually these surnames became synonymous with the family rather than the occupation, which made Smith an extremely common name within Medieval society that has survived to this day.