Ceuta and Melilla
As the provincial Surname distribution map (above) indicates, Mohamed is an often-occurring surname in the autonomous Mediterranean North African cities of Ceuta and Melilla (respectively registered 10,410 and 7,982 occurrences), due to immigration from Morocco. Hispanophone Muslims use the Spanish "Mohamed" spelling for “Muhammad”. As such, it is often a component of Arabic names for men; hence, many Ceutan and Melillan Muslims share surnames despite not sharing a common ancestry. Furthermore, Mohamed (Muhammad) is the most popular name for new-born boys, thus it is not unusual to encounter a man named Mohamed Mohamed Mohamed: the first occurrence is the name, the second occurrence is the paternal surname, and the third occurrence is the maternal surname.
Read more about this topic: Spanish Naming Customs, Spain's Other Languages