There's an interesting point regarding Treerazer that, while it's kinda pedantic and silly, it's still neat enough to point out:
Jacobs went out of his way to make it "Treerazer" as something that 'razes' forests and the natural world, a "razer" -- someone who razes.
And he has pointed out that if it were "Treerazor" it would be someone who gives trees a nice clean shave, like at a 'Barber Shop.' So before the Ents go to war in Middle Earth, perhaps they want to get a razor and trim-and-shave their 'tree-beards' a little. Make 'em all nice and tidy.