I have hobbed and nobbed with my friends in most of their rat-traps, and know the geography of them.
"side of fireplace," 1670s, alteration of hubbe (1510s), of unknown origin, perhaps somehow related to the first element in hobnail.
"clown, prankster," short for hobgoblin (q.v.). Hence, to play (the) hob "make mischief" (by 1834).