Tertullian
Tertullian of Carthage was the first major Christian theologian to write in Latin, and he shaped the language the Western Church still uses — he was the earliest writer known to call God a trinitas, a "Trinity." His Apology answered the pagan charges laid against Christians, while treatises such as Against Praxeas and the Prescription Against Heretics defended and defined Latin doctrine. Drawn in later life to the rigorist Montanist movement, he was never canonized — yet his influence on Western Christianity is hard to overstate.
Jerome records that Cyprian of Carthage — the next great Latin Father — never passed a day without reading Tertullian, and that when he wanted the book he would simply say, Give me the master, meaning Tertullian. No portrait or relic of him survives; that one line is the measure of his authority.
Known for
The blood of the martyrs
“The oftener we are mown down by you, the more in number we grow; the blood of Christians is seed.”
The close of his Apology, addressed to the persecuting authorities — better known in the paraphrase "the blood of the martyrs is the seed of the Church."