What is the etymology of the term "Nuclear Polynesian Language"?

Recently, (when looking up the etymology of Hawaii), I came across the Nuclear Polynesian languages (See: https://en.wikipedia.org/wiki/Nuclear_Polynesian_languages).

I am now curious as to the etymology of this language family itself. Specifically: Where does the term “Nuclear” in “Nuclear Polynesian” come from? Does this refer to the nuclear tests that took place in the region in the mid-to-late 1900s? Or might it refer to a region acting as a 'nucleus', from which these languages spread out?

I have not been able to find any information about this online, including wiktionary and etymonline, other than this Quora article which does not really answer my question: (https://www.quora.com/Why-are-some-Polynesian-languages-called-Nuclear-Polynesian-languages).

The wikipedia article you cited says (emphasis by me):

The contemporary classification of the Polynesian languages began with certain observations by Andrew Pawley in 1966 based on shared innovations in phonology, vocabulary and grammar showing that the East Polynesian languages were more closely related to Samoan than they were to Tongan, calling Tongan and its nearby relative Niuean "Tongic" and Samoan and all other Polynesian languages of the study "Nuclear Polynesian".

It follows that "nuclear" here is used to denote a "core"/"nucleus" and as an opposite of e.g. "peripheral".