Usually, though, the names plain and simple mean something. That's what we run into in Genesis 4:1-2. Adam and Eve have kids -- two boys. And their names mean something that becomes crucial to the story, but we don't speak Hebrew (most of us) so we don't get this part of things. "Cain" means "produced" or "production." So Eve says "With the help of the Lord I have produced a man." It is interesting to note that this is the first time (after the little fig leaf incident, which doesn't really count) that humans have produced anything. Tuck that in your hat for the moment.
By the way, let's take a short detour. Just for the record, there is no basis for the often-cited argument that sex is somehow linked to Adam and Eve's sin, that in the garden prior to the fall there was no sex. A God-given relationship that includes physical intimacy is laid out very clearly in Genesis 2:24-25. We get ashamed about our sexuality not because it's sinful, but because so often we indulge it outside what God intends. Within the boundaries God sets for sexual expression, it is an amazing, wonderful gift.
What about this second son? Abel's name doesn't even get explained in the text. That's because in Hebrew, there's not even a joke being made -- it's just a Hebrew word. "Abel" means "Empty." Adam and Eve had two boys, "Productive" and "Empty."
Now before you start to feel bad for Abel, think ahead -- better yet, read ahead -- to the part where they both offer sacrifices to God. One of the mysteries in the Bible is why Cain's sacrifice isn't accepted. Is it possible that Cain is full of himself and what he has produced? That he brings an offering to God out of his productivity and thinks God should be impressed? What about Abel, then -- is Abel's offering accepted because he comes empty of himself?
Try this. First, take a look at Psalm 51:17 and see what it says about the way we bring offerings to God. And check out Isaiah 57:15 and dozens of other verses that talk about God's attitude toward those who are contrite, beaten down, humbled. Or read the Beatitudes of Jesus in Matthew 5. It's also interesting to do a keyword search through the Bible on two words. First do the word "empty" and see how often God has to empty out something with which we have filled ourselves. Our wealth, our pride, our self-assurance, our security, our arrogance -- God needs to empty us of all these things. Then look at the word "filled" and see what God wants to fill us with. Recognize that you can't be filled with the things of God if you're already full of yourself.
Sometimes the most simple lessons are the easiest to miss.