One of my biggest pet hates is the incorrect use of plurals for Maori words. One very common case of this is the use for those in Wellington is the use of the of the word "Rimutakas" to describe the Rimutaka hill road. Even NZTA ads on the radio right now talk about "roadworks on the Rimutakas".
There was debate last year over Rimutaka actually not meaning anything in Maori (it should be Remutaka) but it doesn't change the fact that people are trying to make a Maori word a plural, something the language doesn't have.
Even in English it makes no sense making it a plural - there is only one hill and one mountain range!
I could fix that! Let's rename it the Hillary Range instead....