As De Callusio, and Callusu, we first see this surname documented in Malta on the Militia Roster of 1417.
There are two potential Italian sources for this surname, the first is calloso, meaning “hard-skinned” and may refer to a callous, heartless person. The other is the Gallùs, from gallo, meaning “cock, rooster”. Indeed a branch of the Callus family incorporates a rooster on their crest. A final potential source, much like Calleja, may be the Greek kallos, meaning “graciousness, beauty”.
This coat of arms displays a chapel with a patriarchal cross, perhaps hinting at a connection with the Levant.