What does "NDA" stand for in Eikon "NDA_RAW" data?

It doesn't stand for anything meaningful to the user. The acronym refers to the name of a backend system that houses certain data assets including end of day timeseries. The view NDA_RAW represents the timeseries in the data model used in NDA, as opposed to other views that provide certain normalization on top of NDA data model, including for example the grouping of open, high, low, close values.