(From the YouTube Description)
"O Sacred Head, Now Wounded" is a Christian Passion hymn based on a Latin text written during the Middle Ages.
The hymn is based on a long medieval Latin poem, Salve mundi salutare, with stanzas addressing the various parts of Christ's body hanging on the Cross. The last part of the poem, from which the hymn is taken, is addressed to Christ's head, and begins "Salve caput cruentatum." The poem is often attributed to Bernard of Clairvaux (1091-1153), but is now attributed to the Medieval poet Arnulf of Louvain (died 1250). It was used for the text of Dieterich Buxtehude's Membra Jesu Nostri,
The last part of the poem was translated into German by the prolific Lutheran hymnist Paul Gerhardt (1607-1676). The German hymn begins, "O Haupt voll Blut und Wunden".
The hymn was first translated into English in 1752 by John Gambold (1711-1771), an Anglican vicar in Oxfordshire. His translation begins, "O Head so full of bruises." In 1830 a new translation of the hymn was made by an American Presbyterian minister, James Waddel Alexander (1804-1859). Alexander's translation, beginning "O sacred head, now wounded," became one of the most widely used in 19th and 20th century hymnals.
Another English translation, based on the German, was made in 1861 by Sir Henry Baker. Published in Hymns Ancient and Modern, it begins, "O sacred head surrounded by crown of piercing thorn."
In 1899 the English poet Robert Bridges (1844-1930) made a fresh translation from the original Latin, beginning "O sacred Head, sore wounded, defiled and put to scorn." This is the version used in the Church of England's New English Hymnal (1986) and several other late 20th-century hymn books.
The English Hymnal, 1906 has a translation atrributed to "Y.H."
The music for the German and English versions of the hymn is by Hans Leo Hassler, written around 1600 for a secular love song, "Mein G'müt ist mir verwirret", which first appeared in print in 1601. The tune was appropriated and rhythmically simplified for Gerhardt's German hymn in 1656 by Johann Crüger. Johann Sebastian Bach arranged the melody and used five stanzas of the hymn in his St Matthew Passion, stanza 6 also in his cantata Sehet, wir gehn hinauf gen Jerusalem, BWV 159. Bach used the melody on different words in his Christmas Oratorio, both in the first choral and the triumphant final chorus.