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.
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"?