What is the origin of ex-voto?

Ex-voto, “out of a vow (fulfilled or undertaken),” refers to a painting or other artifact left as an offering in fulfillment of a vow or in gratitude, e.g., for recovery from an illness or injury. Ex-voto being a Latin phrase, such offerings are therefore associated with Western Christianity, especially with Mediterranean Catholicism (Italy, Iberia, former Spanish colonies abroad). (The Greek Orthodox Church has a similar custom; the offerings in the Greek Church are called támata, plural of táma “a vow, an ex-voto offering.”) The custom antedates Christianity by many hundreds of years: In the Iliad Hector says he will hang the weapons of his foe in the temple of Apollo; the poet Hesiod dedicated the tripod he won in a poetry contest in Chalcis to the Muses on Mount Helicon. Miltiades, the general of the Athenians and their Plataean allies at the Battle of Marathon (490 b.c.), dedicated his helmet in the temple of Zeus in Olympia (where his helmet is on display on the archaeological museum). Even the witty, urbane Horace refers to “the sacred wall with its votive tablet [tabulā… vōtīvā] shows where I have hung my sodden garments in gratitude to the god of the sea” (for escaping the surely destructive shipwreck of a love affair). Ex-voto entered English in the first half of the 19th century.