Don’t judge what a tankie or Nazi is by insults on the internet, hyperbole and bullshit rule.

Words are defined by common use. If the common use of the word "tankie" is to throw it at people who oppose war, then that's what it means now. You can say it's defined as being pro- war, but I've never seen it used that way.

Back in the day when word originated they loved the T-34 tank and Russia in WW2 and so on.

Well sure, WWII is basically the go-to example of a necessary and justified war. There was a time in my life when I labelled myself as a pacifist and the counter-example that everyone always brought up was WWII.

At that time, my position was that that was one exception from like 70 years ago and we shouldn't make a rule from the exception considering how many unjustified wars have been fought since then. Now, my position is a little bit more flexible and moderate to account for that and a handful of other cases: now I say, "no war but class war," and WWII was a class war.

However, my position hasn't actually changed much in practice since those days. The vast majority of wars and violence are systemic and fought for bourgeois interests, so I still oppose them. Only very rarely does violence happen in the opposite direction, for example if we compare the death tolls of Luigi Mangione to Brian Thompson.

And what do you think the “tank” in “tankie” comes from?

It comes from accusing people who oppose war of supporting the other side's tanks, as I just explained to you in my previous comment.