... Church switched to the closest thing [to the caret ^], an uppercase lambda, Ax(x + x). The A was easily confused with other symbols, so eventually the lowercase lambda was substituted... #JohnMcCarthy was a student of Church's at Princeton, so when McCarthy invented #Lisp in 1958, he adopted the #lambdaNotation.
#AlonzoChurch #Notation now back to #CaretNotation for #Racket??
(define-syntax ^
(make-rename-transformer #'λ)) ; or ; #'lambda
((^ (x y) (expt x y)) 3 4) ; 81