Emanuel: The Spanish word here is a personal name transliterated from Hebrew, meaning "God is with us." The same name is used in English with various spellings.
Desterrado: The adjective desterrado is derived from the noun tierra, meaning Earth. In this context, it means "exiled," referring to someone removed from his or her homeland.
Vara de Isaí: A vara is a rod or stick. Isaí is a shortened form of the name Isaías, or Isaiah. The reference here is to the Old Testament book of Isaiah, which says in chapter 11, verse 1, that a there "shall come forth a rod out of the stem of Jesse." Christians have interpreted this as a prophesy of the Messiah. In the English translation of this hymn, which is believed to have been written originally in Latin, the line is "Come O rod of Jesse's stem."
Aurora: The aurora is the first light of dawn. In the English translation, the word Dayspring is used here.
Alumbrar: This verb means to enlighten or to give light.
Disipar: Although this verb can be translated as "to dissipate," in the context of this song it is better translated as "to get rid of" or "to dispel."
Oscuridad: It shouldn't be surprising that one meaning of this noun is "obscurity." But it more often means "darkness."
Llave de David: This phrase, meaning "key of David," is a reference to an Old Testament verse, Isaiah 22:22, which Christians have understood to refer symbolically to the authority of the coming Messiah.
