The feast of Corpus Christi, celebrated today on the Ordinary Calendar in the U.S., was established in 1264. The major holy day associated with the Eucharist is Thursday in Holy Week, the day of the Last Supper, but there's a lot that goes in Holy Week, of course, and on Holy Thursday itself, and so this feast was established so that there would be a holy day devoted entirely to the Eucharist. The Pope at the time Urban IV, is said to have asked Thomas Aquinas to write the Mass, and this is very likely the case. It is entirely for this reason that we have several hymns written by Aquinas. Most people wouldn't not have associated poetry with the scholastic saint, but there's general agreement that the hymns for the Corpus Christi mass are extraordinarily good, and they have become some of the most popular Catholic hymns. The hymns in question are "Pange lingua gloriosi," the last part of which, the "Tantum Ergo," is sometimes also used as a stand-alone hymn; "Verbum supernum prodiens," the last part of which is also sometimes used as a stand-alone hymn, "O Salutaris Hostia"; "Sacris solemniis"; and "Lauda Sion Salvatorem". Of these, the "Pange lingua" is most famous; only in the separate "Adoro te devote" does he surpass its quality.
The translation (my own and very rough):
Sing, my tongue, of the glorious
mystery of the Body
and of the precious Blood,
in which the price of the world,
the fruit of generous womb,
the King of Nations, flowed forth.
For us given, for us born
from the untouched Virgin,
He dwelt in the world
after the seed of the Word was sown;
his enclosure ended the wait
with marvelous order.
On the night of the Last Supper,
reclining with His brothers,
having fully observed the Law
with the lawful meal,
He as food to the crowd of the Twelve
gave Himself with His own hands.
Word made flesh the true bread
into flesh makes by His word
and wine becomes the Blood of Christ.
Even if the senses fail,
to establish sincere heart
faith alone suffices.
Such sacrament we therefore
reverence, bowing down,
and the ancient covenant
gives way to a new rite:
Faith stands as a supplement
to the failure of the senses.
To Begetter and Begotten
praise and jubilation be,
strength and honor, might as well,
and also blessing be;
and to the one who proceeds from both
equally be the praise.
The following is a somewhat pop-ish version of "Pange lingua", albeit famous in its own right, by the Spanish group Mocedades. It has the first three stanzas and part of the last stanza. The first guy accidentally slides off into the wrong lines, but they recover, as professionals do; the crowd, if they noticed any difference in the Latin at all, probably thought they were just doing a variation.
You can hear Mocedades' original version here.