ROFL, yeah, it’s weird, isn’t it. I remember hearing about Limbo too, but I can’t remember EVER learning where the idea came from. It just was. By the way, it was explained to us, exactly as you described it (Limbo). The babies can’t get to heaven (unbaptized) but can’t go to purgatory or hell either (because they were innocents).
Sending newborn infants to hell, or sending “heathens” (those who never had a chance to hear “Good News”) would sure as shit blow away the concept of a loving and merciful God. And what about the zillions of people who lived and died in all those years before Jesus arrived? They go to hell for the high crime of poor timing and bad luck? There are too many holes in the claim that all unbaptized people are roasting in hell. I better stop. Every question would lead to so many other related questions.