The convent where Olive Snook is staying is called the "Sisters of the Divine Magnatum". The Sisters dig and sell truffles to raise money for the convent. 'Tuber Magnatum' is the Latin name for the Italian White Truffle, the most prized of truffles.
This episode's look mirrors "The Black Narcissus" a classic english movie by the Powell/Pressberger team with wonderful shots by cameraman Jack Cardiff. While retaining the fast paced hilarious concepts of the series and this episode in particular, this show still manages to pull off a great homage to a great movie.