Who coined the term “horsepower” for the first time?

Answer

The term ‘horsepower’ was borrowed from English, where the concept of ‘horsepower’ was probably introduced by James Watt around the end of the eighteenth century. The Dictionary of the Dutch Language (WNT) cites a letter from 1823 as the oldest reference in Dutch, but even older examples can be found in the huge collection of Google Books: in his “Journey through England, Walles and Scotland, done in year 1816” Samuel Heinrich Spiker already mentions steam engines “of six horsepower” (p. 55). The term appeared regularly in newspapers from the 1820s onwards, suggesting that the word entered our language somewhere around the beginning of the nineteenth century.