The etymology of religion appears to derive from the Latin religare which means to bind. I became aware of this word origin while reading the page turning The Faith Instinct by Nicholas Wade.
Wade points out religion emerges when people signal to each other their commitments to the shared beliefs that bind them together as a community.
This binding together has a darker side that can lead to zealotry and fanaticism. As an example considered the murderous actions of Paul Hill who believed he was carrying out the will of God when he gunned down an abortion doctor and his bodyguard.