I think it's a plurale tantum https://en.wikipedia.org/wiki/Plurale_tantum https://en.wikipedia.org/wiki/Plurale_tantum That is, it seems to be grammatically

I think it's a plurale tantum https://en.wikipedia.org/wiki/Plurale_tantum https://en.wikipedia.org/wiki/Plurale_tantum That is, it seems to be grammatically plural but not have a distinctive singular. 4. pl. A piece of real estate; a building and its adjuncts; as, to lease premises; to trespass on another's premises. [1913 Webster]