We often use the word roots when referring to the solutions of an equation. For instance, when we have a polynomial $P(x)$, we call its zeros the roots of $P(x)$.
For some polynomials we can relate the zeros with a root function of some kind, say $$ x^2-4=0, $$ we can take the square roots of $4$ to get the solutions. However with some functions, like trigonometrics, there doesn't seem to be a clear relation with the typical root functions.
I ask because in an assignment I gave, students where asked to find the roots of a rational function. I found out that many students had never heard the word roots used in a "find the zeros" context. Many of them took the square roots of the function and tried solving some equations that made no sense.
When looking online, I could not find any solid reference to the first uses of the word in that context.