The "hob" I first ran across was related to hobilar, a mounted medieval infantryman (sometimes referred to as a light cavalryman although they fought dismounted). A hobby btw is an active medium sized horse in medieval English. To "hobble" someone, or animal, is to prevent free movement. Hobilars either hobbled their horses to fight on foot or every 4th man held the horses.
I've seen the hearth reference, either Welsh or Old English, too of course, as well as "hob" or "hobin" being a short for Robert. Later "Rob" or "Robin" which makes more sense to modern ears...
Personally I find the connection of Hobgoblin (a trouble making Goblin also something to be dreaded) to Goblins and the term Bugbear (again something dreaded as well as a fey / goblin) interesting. A Goblin being the basic humanoid monster, the Hobgoblin being more dangerous and the Bugbear being the most dreaded version (which related the usage of hobgoblin and bugbear as something feared).
For me, in my adolescent mind (in the mid seventies), I connected hobgoblin to hobilar and it made sense for the hobgoblin to be a soldier-goblin. And that's what they have been in my game ever since. Larger, more militarized, and disciplined Goblins. Which is largely the D&D / PF take on them as well.
Given the multiple, and twisted, variations of "hob" just settling on something that makes sense in your own game, that has meaning in your own game world, is all you can really do. Well, and discuss the possibilities on message boards :)