Etymology
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Lares (n.)
Roman tutelary gods and household deities, worshipped in primitive cult rites, Latin, plural of Lar, a word of unknown origin. Infernal, protective of the state and the family, they could be potently evil if offended. Their shrine in the home was a lararium.
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Penates (n.)

Roman household gods (often paired with the Lares), 1510s, from Latin Penates "gods of the inside of the house," related to penatus "sanctuary of a temple" (especially that of Vesta), cognate with penitus "within" (see penetrate). They presided over families and were worshipped in the interior of every dwelling.

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larva (n.)

1630s, "a ghost, specter, disembodied spirit" (earlier as larve, c. 1600), from Latin larva (plural larvae), earlier larua "ghost, evil spirit, demon," also "mask," a word from Roman mythology, of unknown origin; de Vaan finds a possible derivation from Lar "tutelary god" (see Lares) "quite attractive semantically."

Crowded out in its original sense by the zoological use (1768) which began with Linnaeus, who applied the word to immature forms of animals that do not resemble, and thus "mask," the adult forms.

On the double sense of the Latin word, Carlo Ginzburg, among other observers of mythology and folklore, has commented on "the well-nigh universal association between masks and the spirits of the dead."

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