Oh, teaching! "prick" was always good for a snigger, but the best / worst was from the poem "Flannan Isle", where the strange birds are "far too big for cormorant or shag".
I used to give the an advance warning: "Right! In this poem the word "shag" will occur. It means..... But knowing you lot let's have a snigger now." It usually worked, apart from those students who wanted to explore the etymology of the word...
To obliterate your address on packaging