Derived from 'Mammalucco', a word in Neapolitan and other southern Italian dialects meaning 'a crazy, savage, or stupid person'. Used amongst Italo-Calfornians, it is generally used to the same context but more so as an endearing insult applied to a comical mishap or stupidity on the recievers behalf.
'You spilled the wine...ya LUC!'
'You're a luc'
'Joe is such a luc, he has been lost for an hour'
'Don't be a LUC!!!'