From line 166 of org-entities.el on the master branch, commit f685535 (it goes back to the first commit).

("Delta" "\\Delta" t "Δ" "Delta" "Gamma" "Δ")

diff --git a/lisp/org-entities.el b/lisp/org-entities.el

index 7ef0524..51f5a06 100644

--- a/lisp/org-entities.el

+++ b/lisp/org-entities.el

@@ -163,7 +163,7 @@ packages to be loaded, add these packages to `org-latex-packages-alist'."

("beta" "\\beta" t "β" "beta" "beta" "β")

("Gamma" "\\Gamma" t "Γ" "Gamma" "Gamma" "Γ")

("gamma" "\\gamma" t "γ" "gamma" "gamma" "γ")

- ("Delta" "\\Delta" t "Δ" "Delta" "Gamma" "Δ")

+ ("Delta" "\\Delta" t "Δ" "Delta" "Delta" "Δ")

("delta" "\\delta" t "δ" "delta" "delta" "δ")

("Epsilon" "E" nil "Ε" "Epsilon" "Epsilon" "Ε")

("epsilon" "\\epsilon" t "ε" "epsilon" "epsilon" "ε")