[William Cloud Hicklin]

I don't imagine Eomer knew much of anything about Elves or Dwarves or their abilities. He had never seen one, nor I expect ever met anyone who had (save perhaps Gandalf). He was aware of Lorien, but is plainly ignorant of its inhabitants. Some other Rider at Helm's Deep says "Dwarves are cunning folk with stone, *they say*," which implies a very rudimentary, rumour-based awareness of the Naugrim.

It's noteworthy that "Wingfoot, I name thee" is addressed specifically to Aragorn, the Man. He doesn't apply it to the other two, mysterious creatures whose folk weave magic camouflage cloaks.