Genesis 4:1

Through God. Hebrew may signify also: "even God," as if she thought this was the promised seed, who, as Onkelos paraphrases it, would serve the Lord. (Calmet) --- So little could she foresee the future conduct of Cain, whose name may be derived either from kone, possession and acquisition, or from kun, lamentation. The latter interpretation would have been better verified by the event, and the name of Abel, vanity, or sorrow, for which his parents allege no reason, might also have been reversed, on account of his justice, for which he is canonized by Christ himself, and declared the Just. Pious and significant names were imposed by either parent. Cain was the second man. He was not conceived till after the fall, and was therefore the first born in original sin. (Haydock)