thumb|upright|Cover from [[Naturalis Historia from Pliny the Elder, the work that could have involuntarily been the origin of the mythical character Lusus.]]
Lusus, in Roman mythology, is a son or companion of Bacchus, god of wine and divine madness. In Portuguese culture, Lusus features in national mythology as the founder and namesake of ancient Lusitania and the father of the Lusitanians, traditional ancestors of the modern Portuguese people.
Origins of the name
With the Roman conquest of the Iberian Peninsula (between 219 and 17 BC), the Roman province of Lusitania was established, broadly in what is today Portugal south of the Douro river together with Extremadura in Spain. There are no historic records of the eponyms Luso or Lusus amongst the Pre-Roman peoples of the Iberian Peninsula (in this specific areas, Celts or pre-Celts).
The etymology of Lusitania, like that of Lusitani, is unclear. The name may be of Celtic origin, or derive from Lucis or Lusis, an ancient people mentioned in Avienius's Ora maritima (4th century AD, but drawing on the Massaliote Periplus of the 6th century BC).
Origins of the mythological character
The entire character of Lusus in fact seems to derive from a mistranslation of an expression in Pliny's Naturalis Historia. Pliny writes: "M. Varro informs us that... the name 'Lusitania' is derived from the games (lusum) of Father Bacchus, or the fury (lyssam) of his frantic attendants, and that Pan was the governor of the whole of it." The mistake would have been in the interpretation of the word lusum as a proper name ("Lusus") rather than as the common noun meaning "games": thus "lusum [...] liberi patris" becomes "Lusus of father Bacchus" rather than "the sportiveness of father Bacchus." The resulting interpretation made "Lusus" a companion or son of Bacchus. It is this interpretation that is seen in Luís Vaz de Camões's Lusiads (canto III, strophe 21):
:Esta foi Lusitania, derivada
:De Luso, ou Lysa, que de Baccho antigo
:Filhos foram, parece, ou companheiros,
:E nella então os incolas primeiros.
:This Lusitania was; in whom we greet
:Lusus, or Lysa, who the offspring were,
:Or friends, of ancient Bacchus, as appears,
:And her first dwellers in her earliest years.