~ this simple symbol is tilde ~
Tilde comes from Latin Titulus.
While it's used sometimes to indicate tones and accents it was first developed to mark palatal nasals.
Like the Cedilla it begun life as a scribal shorthand in the European Middle Ages.
Ancient Latin doesnt seem to have had an "NG" sound and Greek writes ng as gg.
However later Romance and other European languages developed a full range of palatals and nasals we do not have in English.
Spanish scribes used a tilde over n to show the "ny" sound.
From Spanish it was borrowed to show in some languages that there was NO nasalization of a vowel or that a nasalized vowel had replaced an earlier nasal sound that had disappeared as in Brazilian and Continental Portugese and Frnech.
Other languaes that mark a palatal nasal with a tilde are apart from Castilian Spanish, Asturian, Basque, Talalog,Galician, Guarani, Tetum and Papaimento.
Tilde a simple squiggle of a sign has now migrated to Asia and the Americas and even has special functions in IPA.
More about diacritics and nasals soon.