The term "critical race theory" was absent from the corpus of literature in the 1970s. See in particular this plot:

https://miro.medium.com/max/1704/1*fLHX4a2R6Kwa1jR5O0Bcnw.png

While key figures were working in the area of law, early writings within the movement were not confined to the field of law, nor did the movement remain contained within the field of law.

https://aninjusticemag.com/what-is-critical-race-theory-19dbaf2bf33a