Elfin Grot means: 1 Covert crack-house that specializes in magic mushrooms. This is what John Keats refers to in ‘La Belle Dame Sans Merci,’ where he expresses his passion for narcotics. Another interpretation states that the Elfin Grot’ represents the castle where La Belle Dame seduces her knight. John Keats, a smackhead, could be another interpretation. 2 A name that is given to the vagina of a witch. (in Community Dictionary, added by Yolanda Santana)