Background:
The least-squared error fit has been around for some time.
Laplace, P. S. "Des méthodes analytiques du Calcul des Probabilités." Ch. 4 in Théorie analytique des probabilités, Livre 2, 3rd ed. Paris: Courcier, 1820.
Gauss, C. F. "Theoria combinationis obsevationum erroribus minimis obnoxiae." Werke, Vol. 4. Göttingen, Germany: p. 1, 1823.
Wikipedia attributes Gauss and Legendre for it. (link)
Many software tools perform basic linear fits with analysis of quality of fit. (JMP, R 'lm', ...)
There is a 200 year span between 2020 and 1820. Somewhere in there the details were added.
Question:
Who is the effective "father" (or mother) of the analysis as we know it?
There has to be someone "back in day" who made the "first" that is ~80% (or more) like what this foundational analysis method?
Can you give a reference to this "first work"?