What I think is really interesting is the number of words that share just a couple of letters -- not whole root words -- but have similar meanings. For instance, words that start with GL have to do with light:
Glow, glisten, glimmer, glass, glare, glint ...
So do words with FL:
Flash, flicker, flare ...
Words with GR have to do with earth:
Ground, grave, grass, grow, aGRiculture ...
And so on. I like to imagine that those little word fragments date back to caveman days. Like maybe back then they grunted "GLLL" when they saw a light, or "GRRRR" to indicate the ground.