It has long been assumed that Corpus Christi was simply taken from Corpus Christi Bay, a name itself allegedly conferred by Spaniard Alonzo Alvarez de Pineda, who claimed it for the Spanish Crown in 1519 while mapping the gulf coast. As the story goes, the day Pineda encountered the shallow inlet happened to fall on the feast day of Corpus Christi, a day in the Latin church calendar to emphasize and ritualize the real presence of Christ’s body and blood in the consecrated host. 
The inland Corpus Christi (now the eighth largest city in Texas) did not come into existence until the decade between the Texas Revolution (1835-1836) and the Mexican American War (1846-1848). Not until 1845 or 1846 do maps show an inland place named Corpus Christi in addition to the bay of the same name. 
In fact, in the early part of the 1840s, what is now called Corpus Christi was then called Kinney's Rancho, for a character named Henry Lawrence Kinney who virtually stole the land. When the US set its sights on doing the same thing, i.e., annexing Texas, President Polk sent General Zachary Taylor and his "army of occupation" to the border. They set up at Kinney's place.
Meanwhile, Polk and the pro-annexation parties sounded the drumbeats with rhetoric in which American sacrifice in Texas featured prominently. Corpus Christi, in Latin, means the body of Christ -- the sacrificed body. As annexation propagandists eulogized those killed at the Alamo and at Goliad, they merged Anglo deaths into national destiny, a destiny that could only be realized when America’s identity was clear, and that identity was “most intelligible in contradistinction to Mexico: Protestant, not Catholic; Anglo-Saxon not Indian/Mestizo/Spanish; republican not tyrannical; industrious not slothful.” 
After the Army of Occupation left Kinney's spot to start a war with Mexico, it was henceforth known as Corpus Christi. The name, now consonant with the bay, implied American borders that extended beyond the land to include bays, inlets, rivers, and coastlines. The authoritative power and efficacy of mottoized Latin was long familiar in US national and state seals, such “E pluribus unum,” “Annuit Coeptis,” and “Novus ordo seculorum.” Corpus Christi would have been a familiar bit of Latin, and not just to those with a Catholic background. Further, its evocation of sacrifice subtly underscored other discursive efforts to depict Texas as a site of Anglo sacrifice, and therefore deserving of annexation.
*I discuss this in more detail in a paper published in the journal Names.
 On Pineda, see Donald E. Chipman, Nuño de Guzmán and the Province of Pánuco in New Spain, 1518–1533 (Glendale, California: Clark, 1967) and Robert S. Weddle, Spanish Sea: The Gulf of Mexico in North American Discovery, 1500–1685 (College Station: Texas A&M University Press, 1985).
The Center for Texas Studies at Texas Christian University, Going to Texas: Five Centuries of Texas Maps (Fort Worth: Texas Christian University Press, 2007).
 John Pinheiro, Missionaries of Republicanism: A Religious History of the Mexican American War (New York: Oxford University Press, 2014), 65.