I think you should call it `'parzen'` since this is Parzen's 1963 estimator. And reference that paper,
http://www.stat.tamu.edu/~eparzen/parzenbook/SpectralAnalysisMissingObservations.pdf

and possibly

http://www.cirje.e.u-tokyo.ac.jp/research/dp/98/f1/dp.pdf

which also contains two other estimators.