The -lin element of this name is difficult to translate precisely; it comes from the Elvish word for 'sing', and refers to the musical sound made by this river as it flowed.

In his linguistic appendix to The Silmarillion, Christopher Tolkien suggests a different derivation, based on a distinct lin element meaning 'pool' or 'mere', but volume XI of The History of Middle-earth is quite explicit about the musical connotations of the name.

This variance seems to be due simply to later material coming to light after the publication of The Silmarillion. Commenting on the same source in The History of Middle-earth, Christopher Tolkien notes that Teiglin was probably not the latest form of the name's spelling, and that the published Silmarillion should perhaps have presented it as Taeglin (which would be pronounced 'tie-glin' rather than 'tay-glin').