Also Alan Kay and the Xerox PARC team designed Smalltalk (as Papert did before with Logo) with profound human-centered considerations, and they even "tested" their early concepts with children.
Also some other languages explicitly state human-centered design goals (e.g. Python, Eiffel), but as with Pascal or Ada the approach was more based on expert judgment, formal analysis, and established principles, not practical studies.
People who’ve spent a long time programming have spent a long time optimizing everything about their work, and they’re willing to talk about it (most of them won’t shut up about it, even).
They may not have used standards such as the gp comment mentions, but they definitely considered human factors a lot.
E.g. TIMTOWTDI - There Is More Than One Way To Do It.
But that's not the only area in which they applied it.
Yes. In fact, in the early days, there were tools with names like sed2perl and awk2perl, or similar, IIRC. And those could convert code between their respective source and target languages.
And even easier if you know C and Unix.
A far more important measure is something like function points per month of developer time. See page 49 of https://www.ifpug.org/wp-content/uploads/2017/04/IYSM.-Thirt... for some data on that. ADA 95 did pretty well, around 11. Perl beat it with 15.
Of course that measure isn't perfect. Excel trounced both with over 30. But Excel is only appropriate for some kinds of projects.