It’s got a lot of significance, Biblically.
It’s not “relax,” it’s not that we have to stop doing things in order to rest. It seems more like a state of mind, a spiritual place. God says we can enter into his rest. He rested on the seventh day. It’s about realizing you don’t need to work all the time in order to get everything done. I think it has a lot to do with trusting God, and being aware of that.
Jesus took time out to pray to the Father, I think that meant rest. I think he was able to keep going, even when people were all around him, and even when they thwarted his time alone, because he was spiritually resting in His Father.
Yea, I need to do some more research, but a woman at work the other day “had a word for me” and it was “rest.” :)