'What's the context for the use of "folksong", out of interest?'
.,,.
'William John Thoms (November 16, 1803 – August 15, 1885) was a British writer credited with coining the term "folklore" in the 1840s. Thoms's investigation of folklore and myth led to a later career of debunking longevity myths. ... Thoms is credited with inventing the word 'folklore' in an 1846 letter to the Athenaeum.[citation needed] He invented this compound word to replace the various other terms used at the time, including "popular antiquities" or "popular literature". He was fond of the works of Jacob Grimm, which he considered remarkable.'   Wikipedia