1846, "pertaining to or formed by the glottis;" see glottis + -al (1). Glossal is attested from 1860.
Entries linking to glottal
glottis n.
"mouth of the windpipe, opening at the top of the larynx," 1570s, from Greek glōttis "mouthpiece of a pipe," from glōtta, Attic dialect variant of glōssa "tongue" (see gloss (n.2)).
-al 1
suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).