E. Rossoni notes that this surname is typical of the Catanzaro area, in Calabria, and documents its transformation into a surname from a deed of donation of the count of Calabria and Sicily, Roger, to the diocese of Mileto in 1086, where a Nicolaum Sillopem cum filis is mentioned.

P. Durante proposes a Greek origin for the surname, although the etymology he suggests —linked to a Greek feminine and to a hypothetical form thelupus— appears incomplete and without sufficient development to be evaluated with precision.