Origin
The Abecasis and Abecassis family names seem to have the same origin. The name means "father of Cassis" and seems to have come from the tribe of the children of Benjamin. They occupied the Cassis (or Casis) valley which was
attributed in the division of Palestine (Joshua 18:21). This happened around 1200 BC (more or less at the same time as the Troia war in Greece) after the taking of Jericho and conquest of Palestine.
Joshua 18:21
King James Version
Now the cities of the tribe of the children of Benjamin according to their families were Jericho, and Bethhoglah, and the valley of Keziz.
Revised Standard Version
Now the cities of the tribe of Benjamin according to their families were Jericho, Beth-hoglah, Emek-keziz.
Jerome's (Latin) Vulgate
Fueruntque civitates eius Hiericho et Bethagla et vallis Casis.
Portuguese, from Benedictine Monks of Maredsous (Belgium)
As cidades da tribo dos benjamitas, segundo suas famílias formam: Jericó, Bet-Hagla, Emek-Casis,...
The family name is also connected with ancient and pre-Islamic Arabs.
In Eastern Spain there are some traces of an old city called Becassis which seems to have been founded by a group of
Arabic Jews.
The Abecassis, Aboukassis, Abukassis, Bokassis, Boukassis, Bouquassis and Bukassis came from East to Morocco before the 10th century.
It is also possible that this family name derives from other ethimologies. Cassis (clergyman, religious) was a title used by
Israeli community chiefs in Algeria, similar to "Sheikh", and in
Morocco.
Most of this information on our family origin and history came from "Genealogia Hebraica", by José Maria Abecassis.