[psychoslave]

I get your point on how the words meanings evolves.

Also it’s fine that anyone name things as it comes to their mind — as long as the other side get what is meant at least, I guess.

On the other it doesn’t hurt much anyone to call an oxymoron thus, or exchange in vacuous manner about terminology or its evolution.

On the specific example you give, I’m not an expert, but it seems dubious to me. In x+1=2, terms like x are called unknowns. Prove me wrong, but I would rather bet that Euler used unknown (quantitas incognita) unless he was specifically discussing variable quantities (quantitas variabilis) to describe, well, quantities that change. Probably he used also French and German equivalents, but if Euler spoke any English that’s not reflected in his publications.

[SetTheorist]

"Damit wird insbesondere zu der interessanten Aufgabe, eine quadratische Gleichung beliebig vieler Variabeln mit algebraischen Zahlencoeffizienten in solchen ganzen oder gebrochenen Zahlen zu lösen, die in dem durch die Coefficienten bestimmten algebraischen Rationalitätsbereiche gelegen sind." - Hilbert, 1900

The use of "variable" to denote an "unknown" is a very old practice that predates computers and programming languages.

[psychoslave]

Yes sure, I didn't mean otherwise, but I just wanted to express doubts about Euler already doing so. Hilbert is already one century forward.