I think we've got some confusion of terminology going on here. "Tinned" in this context means copper wire or a connector that has a thin layer of lead/tin solder already applied to it before you buy it.
"To tin" or "tinning" is synonymous with soldering: take bare copper, heat it up, and apply a tin/lead/flux solder to it that melts and spreads out thus coating the bare copper with a layer of solder and sticking it to another piece of copper.
What I meant a couple posts above is to take a piece of precoated copper wire, put it in a precoated lug, place the assembly in a hammer crimp and whack it HARD with a large (hand maul size) hammer. The tin/lead coating is softer than the copper and spreads out and melds together when forcibly put in contact each other. Tin-on-tin crimping is somewhat forgiving of bad crimp technique.
You can tell copper is pre-tinned because it'll have a silvery-gray coating on it. You have to be careful because a silver wire can also be just aluminum and that stuff is just bad news unless you know exactly how to deal with it.
View attachment 2258View attachment 2256View attachment 2257