A hobgoblin is a mythical creature originating from Earth folklore. They were often portrayed as friendly but mischievous little men found within Human dwellings.
Doctor Leonard McCoy has been known to refer to Spock as a hobgoblin. On one such occasion, in 2268, McCoy attempted to show gratitude Spock for saving his life in the City Arena on 892-IV. Spock, however, was preoccupied with trying to find a means of escape from their imprisonment and asked the doctor to "be brief." McCoy replied with "I'm trying to thank you, you pointed-eared hobgoblin!" (TOS: "Bread and Circuses")
The Leonard McCoy of the alternate reality thought of his timeline's Spock as a hobgoblin, as well. In 2258 of that reality, McCoy voiced his extreme displeasure with the Spock's decision to maroon Jim Kirk on Delta Vega for mutiny. Spock showed no remorse for his actions and disagreed with McCoy's assertions, causing an infuriated McCoy to call Spock a "green-blooded hobgoblin." (Star Trek)