Augustine of Hippo

Note that the name Cain means "ownership," which explains what was said at the time of his birth by his father or mother: "I have come into possession of a man through God."

City of God 15.17 ↗

Jerome

And she conceived and gave birth to Cain, and said, I have gained a man from God. Cain, meaning acquisition or possession, is interpreted as κτῆσις in Greek, and expressing its etymology, it is said, Canithi, meaning possession of a man from God. (Ver. 4.) And God looked upon Abel and upon his offerings: but upon Cain and his offerings he did not look. And Cain was very angry, and his countenance fell. …

Hebrew Questions on Genesis ↗

Bede

Now Adam knew Eve his wife, and she conceived and bore Cain, saying: I have acquired a man through God. Henceforth, after the delights of paradise and the guilt of the first transgression, the events of this world and mortal life are narrated, when the first-created, who had been made immortal, after receiving the condition of dying, began to generate mortal offspring from themselves, all conceived in iniquity and brought forth from the womb in sins. …

Commentary on Genesis (Hexaemeron) ↗