"bubonic/pneumonic plague epidemic of 1347-51 in Europe," a modern name, introduced in English 1823 by Elizabeth Penrose's history of England. The contemporary 14c. name for it in most European languages was something like "the great dying" or simply "the plague;" in English it was the pestilence (or, looking back after its return in 1361-2, the first pestilence).
The term "Black Death" first turns up in 16c. Swedish and Danish chronicles, but it is used in reference to a visitation of plague in Iceland (which had been spared in the earlier outbreaks) in 1402-3 that carried off much of the population there. The exact sense of "black" is not clear. The term appears in English translations of the Scandinavian works from 1750s. It was picked up in German c. 1770 and applied to the earlier outbreak and was taken from there into English in that sense.
type of poisonous spider (Latrodectus mactans) in U.S. South, 1904, so called from its color and from the female's supposed habit of eating the male after mating (the males seem to get eaten more often before they mate, when they first enter the webs of the females, which have very poor eyesight). Sometimes also known as shoe-button spider. The name black widow is attested earlier (1830s) as a translation of a name of the "scorpion spider" of Central Asia.