Ancile in Wikipedia
The Ancile, in ancient Rome, is the legendary buckler shield
of the god Mars, said to have fallen from heaven, upon Numa
Pompilius. At the same time, a voice was heard which
declared that Rome should be mistress of the world while the
shield was preserved. The Ancile was, as it were, the
palladium of Rome.
Different authors give different etymologies of this word.
Some derive it from the Greek ἀγκύλος, "crooked". Varro
derives it ab Ancisu, as being cut or arched on the two
sides, like the bucklers of the Thracians, called peltŠ.
Plutarch thinks the word may be derived from the Greek
ἀγκών, "elbow", this weapon being worn on the elbow. The
opinion of Varro, however, is more probable.[citation
Though there was but one Ancile that fell from heaven, there
were twelve preserved, called the Ancilia; Numa, by the
advice, as it is said, of the nymph Egeria, ordered eleven
others, perfectly like the first, to be made. This was so
that if anyone should attempt to steal it, as Ulysses did
the Palladium, they might not be able to distinguish the
true Ancile from the false ones.
These Ancilia were preserved in the temple of Mars, and were
committed to the care of twelve priests of Salii, instituted
for that purpose by Numa . They were carried every year,
in the month of March, in procession around Rome, and on the
30th day of that month, were again deposited in their place.