The city's name is derived via French and Catalan  from the Arabic name ''al-Jazāʾir'' (), "The Islands". This name refers to the four former islands which lay off the city's coast before becoming part of the mainland in 1525. ''Al-Jazāʾir'' is itself a truncated form of the city's older name ''Jazaʾir Banī Mazghanna'' (), "The Islands of the Banu Mazghanna, Sons of Mazghana", used by early medieval geographers such as al-Idrisi and Yaqut al-Hamawi.