Sarumans Orcs

[Saurreg]

As soon as the enemy had gained possession of the eastern end of the Fords there appeare a company of men or orc-men (evidently dispatched for the purpose), ferocious, mail-clad, and armed with axes.

What are these folks then? From the narration, it appears that they are elite troops of Isengard. Both times they were discribed as great - a) The one who hewed Theodred and b) the two who struggled for Theodred's body. Most importantly they were different from the Uruk-hai. If the Uruk-hai were Isengardian grenadiers, then these fell beasts must be its goddamned commandoes.

What are they originally? Do they appear any place else?