in 1936, although in the context of angles between flats the mathematical concept was published by Camille Jordan in 1875.

CCA is now a cornerstone of multivariate statistics and multi-view learning, and a great number of interpretations and extensions have been proposed, such as probabilistic CCA, sparse CCA, multi-view CCA, deep CCA, and DeepGeoCCA. Unfortunately, perhaps because of its popularity, the literature can be inconsistent with notation.