Glasgow Fair was a general holiday for the working classes. It drew large numbers of showmen attracted by the large crowds.

Glasgow Fair pictured in the Glasgow Looking Glass 23 July 1825
Reference: Sp Coll Bh14-x.8 Glasgow University Library, Special Collections
https://www.theglasgowstory.com/image/?inum=TGSB00133
This ballad was sold by The Poet's Box in Glasgow which operated between 1849 to 1911. There were other ‘Poet's Boxes' in Dundee, Edinburgh, Belfast and Paisley and, like the one in Glasgow, each sold similar titles but sometimes had local variations https://libcat.csglasgow.org/web/arena/poets-box