double modal

English Wikipedia has an article on:

double modal

Wikipedia

double modal (plural double modals)

1. (grammar) A sequence of two modal verbs, such as "might could", an impossible construction in standard English, but one used in some dialects, especially Southern US English.
   • 2019, Irina S. Lebedeva, Svetlana N. Orlova, “Semantics and pragmatics of the double modal ‘might could’”, in Training, Language and Culture, volume 3, number 2, →DOI:

     The first instances of double modals date back to the seventeenth century.

• stacked modal

• modal stacking