And where did the ${\displaystyle \psi }$notation come from? (The ${\displaystyle \digamma }$notation seems to be a pretty transparent philological joke.) Double sharp (talk) 09:30, 24 September 2015 (UTC)[reply]

Who invented the function? God, of course. Who was the first mortal human to describe it and give it a name, unfortunately, I can't tell you, but after a brief perusal of the relevant pages, I'd start looking with Gauss and Legendre. --Trovatore (talk) 20:16, 24 September 2015 (UTC) [reply]

Right, of course: that was what I had in mind. Double sharp (talk) 02:37, 25 September 2015 (UTC)[reply]

Wolfram seems to suggest in their PolyGamma article that it was James Stirling in 1730. Here is a link to the work in question, but you will need to know Latin to read it. SpinningSpark 18:28, 25 September 2015 (UTC)[reply]