spruce [LME] Prussia was a former kingdom that covered much of modern northeast Germany and Poland. Between the 14th and 17th centuries it was also known in English as both Pruce and Spruce, and these words could also be used to mean ‘Prussian’.

Spruce was in time used as the name of a type of fir tree imported from Prussia. It was also used in the phrase spruce leather, a fashionable type of leather imported in the 16th century from Prussia and used especially for jerkins. It is probably from this and other such luxury goods that the sense ‘neat or smart in dress or appearance’ developed.