Where does yarn come from, as explained to a four year old who already knows what crochet is:
There are lots and lots of different kinds of yarn, in any color you can think of! Yarn is usually made of lots of littler yarns spun together. Sometimes those smaller yarns are big enough to be yarn themselves (show them super bulky multi-ply yarn, and separate the plies at the end), and sometimes those smaller yarns are tiny (show them sock or lace weight yarn, and separate the plies at the end of the yarn). Some yarns are made of only one strand, but they are still spun.
Spinning is how you turn fiber into yarn. Fiber is what yarn is made of, and it looks like fluff! Like the fluff inside your stuffed animals. You take the fluff, and you spin it between your fingers (demonstrate on your hair or the child’s hair if either of you have long enough hair). My hair doesn’t stay spun into a strand, but yarn is made of different kinds of fibers that like to stick together more*. There are a few different ways people spin yarn; they can use a spinning wheel (add “like from Sleeping Beauty” if the kid knows that story), or a drop spindle, which is kind of like a giant spinning top. The individual fibers are short, but they overlap, and together they form yarn! (optional: “like how your lego building is made up of lots of legos! each strand of yarn is made of lots of fibers”). Then strands of yarn are spun together the same way fiber is spun to make the strands, and you get finished yarn!
There are lots of different kinds of fibers you can use to make yarn. Some yarn is made of plants, like cotton! Your [article of clothing] is made out of cotton. Some yarn is made out of materials that science invented, like acrylic yarns. It’s kind of like plastic, but made a special way to make it lots of soft fluffs instead of hard like [lunchbox/plastic plate/other hard plastic object in sight]. Some yarns are made out of animal fibers! The main animals that people make yarn out of are sheep and alpaca, but you can make yarn out of fur from yaks or rabbits or goats or dogs or a bunch of other fluffy animals. Using animal fiber doesn’t hurt the animals; sheep’s wool grows like our hair grows, but wool is a lot warmer than hair and they grow a lot more of it, so they get really hot in the summer. Farmers cut their wool like we get hair cuts; it’s not painful. Cutting a sheep’s wool is called shearing. It’s important that sheep get sheared because their wool grows all the time, and they can get sick if they don’t get it sheared for too long** (potentially talk to them about/share pictures of Shrek the Sheep). We don’t get sick from having hair that’s too long because people hair and sheep hair aren’t the same, just like your hair feels different than [name of animal they know]’s fur. (if possible, let them touch a bunch of different kinds of yarn)
*I have hair that Does Not Stay in hair ties or braids or any other style I put it in. Idk if other hair type would stay as one strand if you twisted a small lock of hair? if the hair you use to demonstrate spinning does stay, alter the rest of the explanation accordingly
**yes, this is oversimplified. No, I don’t want to explain flystrike to a four year old