This Italian and Spanish surname has Roman pre Christian origins. Recorded in no less than eighty forms ranging from Casa, Caso, Dell Casa, Casillis, Dalla, and Dacca, to Casella, Casetti, Cason and Casaccio, as well as compound locational names such as Casadement, Casajuana, Casanova, Casamoco and many others, this is a residential surname for one who lived in a manor house, or at least the most distinguished dwelling in the relevant town or village. The surname also has aristocratic nameholders, the Counts of Casillis being members of the Spanish nobility. Residential surnames may as in this case, relate to holders of estates, although more usually they are 'reference' names, being granted to them by their neighbours, when they moved from their original village or homestead to another area. To call somebody by the name of their former home being one of the easiest means of identification. The following recordings have been taken from ancient civil and religious registers. They include Hernando de la Casas of San Estaban, Vizacaya, Spain, on February 9th 1573, Magdalena Casa of Olot, Gerona, Spain, on November 27th 1666, Guillermo Casillo at St Catarina, Districto Federal, Mexico, on February 11th 1759, and Adolfo Casajuana christened at the Cathedral, Gerona, on August 31st 1848 The first recorded spelling of the family name is shown to be that of Quitteria Casas, which was dated February 19th 1524, at Medina, Gerona, Spain, during the reign of King Phillip 1st of Spain, Emperor of Mexico, 1516 - 1556.Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.