early 15c., nasale, "of or pertaining to the nose or nostrils," from Medieval Latin, from Latin nasus "nose, the nose, sense of smell," from PIE root *nas- "nose."
Of speech sounds, "uttered with resonance in the nose," attested from 1660s. As a noun, "letter or sound uttered through or partly through the nose," from 1660s. Earlier noun senses were "medicinal fluid for the nose" (early 15c.) and "part of a helmet which protects the nose and adjacent parts" (nasel, c. 1300). Related: Nasalization.
word-forming element making abstract nouns from adjectives and meaning "condition or quality of being ______," from Middle English -ite, from Old French -ete (Modern French -ité) and directly from Latin -itatem (nominative -itas), suffix denoting state or condition, composed of -i- (from the stem or else a connective) + the common abstract suffix -tas (see -ty (2)).
Roughly, the word in -ity usually means the quality of being what the adjective describes, or concretely an instance of the quality, or collectively all the instances; & the word in -ism means the disposition, or collectively all those who feel it. [Fowler]
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Definitions of nasality from WordNet
a quality of the voice that is produced by nasal resonators;