Tsk, all the mix-ups seem silly when they simply could have come over for a cup of tea and just asked you! Or for bacon, the Internet has discovered (of course) that: "The narwhal bacons at midnight" -- Why not? It's as accurate as anything else ever said about them!
Narwhals: not really all that rare.
origin: *Inuit; Qilalugaq qernartaq= "the one that points to the sky", (1650–60) Norse; nár= “corpse” + hvalr= "whale"
Most closely related to the beluga whale, is a small Arctic whale, with a spotty grayish skin that earned it a name from sailors relating it to a "corpse". Although males and females can grow a horn (or two), it is typically a male's single spiraling tooth, which has grown to form the famous unicorn-like spear, from the animal's head, that many recognize as the whale's distinguishing characteristic.
The horn was originally assumed to be used in great sparring matches for female mates, as the males had been seen "fencing" (after proven not to be a figment of anyone's imagination of course), although the native Inuit* people (who were rarely consulted in these matters) assure that the behavior is far gentler and more like rubbing. Which stands to reason in light of a lone dentist's extensive research -- Dr. Martin Nweeia -- leading to the discovery of a great many nerve endings extending through the entirety of the horn, "pointing" to it being a giant sensory device, one likely sensitive to extensive data like temperature, tide, salinity, etc (more studies to follow). And that's...the tooth!
Don't feel too badly, NO ONE believed the first guy who showed up with a stuffed platypus either.