The town's history dates back to 1500 B.C., when Phoenicians occupied a site called Silis, Zili, Zilis, or Zilil ( , ʾšlyt, or , šly) which is being excavated at Dchar Jdid, some 12 kilometers NE of present Asilah; that place was once considered to be the Roman stronghold Ad Mercuri, but is now accepted to be Zilil.