@Setanta,
Indeed, the term "black death" was not used in the Middle Ages - contemporary (German speaking) chroniclers spoke of the "great dying" (
große Sterben) or the "great pestilence" (
große Pestilenz).
The German doctor Justus Friedrich Karl Hecker - under the impression of the currently rampant cholera epidemic - his published in 1832
Der schwarze Tod im vierzehnten Jahrhundert ("The Black Death in the Fourteenth Century") on the 1347-1353 pandemic.
That book attracted a great deal of attention. It was translated into English in 1833 and reprinted several times in the following years.
The terms "Black Death" or "Schwarzer Tod" thus became established as the term for the 14th century pandemic, especially in the English and German-speaking world.