The cosh was the regional dialect which has spoken in the small pockets of the population in the place of Nelanther Isles. Of course the cosh was in a Waelan language language group like the majority of Faerûnian languages and it also used the Thorass alphabet.
Attributes Of Cosh DnD 5E Language
Language Family: Faerûnian languages
Language Group: Waelan
Spoken in: Nelanther Isles
Spoken by: Humans
Based on: Celtic