Parametric polymorphism refers to defining transformations that act ''the same way'' independent of the types involved (?).
The notion of parametric polymorphism originates in the 1969 lecture notes of Christopher Strachey:
Strachey, Christopher. 2000. ‘Fundamental Concepts in Programming Languages’. Higher-Order and Symbolic Computation 13: 11–49. https://doi.org/10.1023/A:1010000313106. [pdf]
@article{strachey_fundamental_2000,
title = {Fundamental {Concepts} in {Programming} {Languages}},
volume = {13},
doi = {10.1023/A:1010000313106},
journal = {Higher-Order and Symbolic Computation},
author = {Strachey, Christopher},
year = {2000},
pages = {11--49}
}