I mean stuff that’s outside. I really couldn’t think of a clever name for this one.
Tree comes from the Old English treo/treow, which means tree, but can also mean wood, timber, log—pretty much anything made out of trees. Amusingly enough, back when Old English had turned into Middle English and treo became tree, there was also a plural for the word: treen. You can’t tell me that’s not hilarious. It comes from the Proto Germanic treuwaz and further back, the Proto Indo European drew-o-, so it’s been relatively stable throughout the past six thousand or so years. It’s also worth mentioning that drew-o- is also the origin word for the word true. Seriously!
Forest on the other hand showed up in the late thirteenth century, usually used as a word for a tree covered area reserved for royalty to go hunt in. It comes from the Old French forest, which just means forest, and it came from either the Late/Medieval Latin phrase forestem silvam, which was to denote royal forests like above, or it comes from the Medieval Latin forestis, which meant something like a game preserve and came from the classical Latin forum (which shockingly enough means forum). Of course, no one’s sure which one of those is right, or if it’s something else entirely.
Grass comes from the Old English graes/gaers, which can mean grass or herb or plant. Further back, it’s the Proto Germanic grasan and Proto Indo European ghre-, which I mentioned long ago as the origin word for green. Well, that was a fast one.
Now it’s time to get dirty, a pun of which I’m greatly ashamed for making. Dirt showed up in the fifteenth century, coming from the Old Norse drit and Proto Germanic dritan. You might have noticed that the i and the r used to be reversed. Well, in Middle English, it was drit/drytt, but apparently people started saying it wrong (a thing called metathesis) and now we have dirt. There’s also the word earth. It comes from the Old English eorÞe (the Þ just means th—remember last week?), which, much like earth, meant either dirt or the entire planet. Further back it’s the Proto Germanic ertho and Proto Indo European er-, which meant earth or ground.
Finally today, we’re looking at soil, which showed up in the early thirteenth century as a verb meaning to pollute with sin, the fourteenth century as a noun that meant an area of land, and then later in the seventeenth century as a word for dirt and sewage (ew!). It comes from the Old French soillier, to dirty, like with mud. It also meant to wallow, because it comes from the word souil, which is a word for a pigsty, and comes from one of two classical Latin words, solium, which can mean throne or bathtub, or suculus, little pig. So because pigs wallow in mud, we have soil.
Tony Jebson’s page on the Origins of Old English