Lord Of The Rings Memes

They didn't seem to use base-12 in general, just a sort of limited application of it in this context specifically. The words "eleven" and "twelve" both derive from "one left (after ten)" and "two left (after ten)", so they seemed to have been thinking of 10 as the base at that scale. And then the long thousand was ten times the long hundred, so that scale was also base-10. The wiki article suggests that it may be a lingering trace of more extensive usage of base-12 that had otherwise broadly been abandoned in favour of base-10