Votum

In ancient Roman religion, a votum, plural vota, is a vow or promise made to a deity. The word comes from the past participle of the Latin verb voveo, vovere, "vow, promise." As the result of this verbal action, a votum is also that which fulfills a vow, that is, the thing promised, such as offerings, a statue, or even a temple building. The votum is thus an aspect of the contractual nature of Roman religion, a bargaining expressed by do ut des, "I give that you might give."

In everyday life, individuals might make votive offerings to a deity for private concerns. Vota privata are attested in abundance by inscriptions, particularly for the later Imperial era. These are regularly marked with the letters V.S.L.M., votum solvit libens merito, noting that the person making the dedication "He has fulfilled his vow, willingly, as it should." William Warde Fowler found in these offerings "expressions of … religious feeling" and a gratitude for blessings received that go deeper than contractual formalism.

During the Republican era, the votum was a regular part of ceremonies conducted at the Capitoline by a general holding imperium before deploying. The triumph with its dedication of spoils and animal sacrifices at the Capitol was in part a fulfillment of such a vow. A general who faced an uncertain outcome in battle might make a votum in the field promising to build a temple out of gratitude for divine aid in a victory. In 311 BC, Junius Bubulcus became the first plebeian general to vow and oversee the building of a temple; he honored the goddess Salus, "Salvation." A vow would also be made in connection with the ritual of evocatio, negotiations with the enemy's tutelary deity to offer superior cult. An extreme form of votum was the devotio, the ritual by which a general sacrificed himself in battle and asked the chthonic deities to take the enemy as offerings along with him.

...
Wikipedia