"The name Cain means "gotten" and is obviously derived from Eve's exclamation of joyful acquisition. The practice of giving names to children associated with some specific event is frequently found in Genesis (4:25; 5:29; 17:5; 41:51; etc.) as well as other parts of the Old Testament. It is significant that this phenomenon in all of the three main supposed “sources” (J, E, P) of the Pentateuch, a fact which itself is strong evidence that all these so-called sources in reality constitute a consistent, unified document reporting real events."
Henry Morris, The Genesis Record, p. 134-135