Meaning

noun an auxiliary verb (such as `can' or `will') that is used to express modality

adjective relating to or constituting the most frequent value in a distribution

adjective of or relating to a musical mode; especially written in an ecclesiastical mode

originFrom Middle French modal, from Medieval Latin modālis (“pertaining to a mode”), from Latin modus (“mode”). Compare to French, Spanish, and Portuguese modal and Italian modale. By surface analysis, mod(e) + -al.

Etymology from Wiktionary, CC BY-SA 3.0