In the The Hobbit, which originally was unconnected with the The Silmarillion, he used the familiar term "goblin" for the benefit of modern readers. By the time of The Lord of the Rings, however, he'd decided that "goblin" wouldn't do - Orcs were not storybook goblins (see above).
Gundabad remained an Orc stronghold, until it was cleared of orcs in TA 2799, after the War of the Dwarves and Orcs. However, small groups of orcs must have returned and fortified it anew during the events of The Hobbit, menacing Wilderland once again.
Uruk-hai was a Black Speech word that meant "Orc-folk". The name "Uruk-hai" has the element Uruk, a Black Speech word related to "orc" and to the (Valinórean) Quenya word urko (Ñoldorin Quenya: orko) of the same meaning. The element hai means "folk", so "Uruk-hai" is "Orc-folk".