(A) translation of the quotation: The notation 波照間 is 当て字; it is generally accepted that the name (波照間) was the corrupted from Hate-no-uruma 果てのうるま, , where "uruma" means corral reef 珊瑚礁 in Okinawa.
(B) 当て字 【あてじ】 (n): "kanji used as a phonetic symbol, instead of for the meaning"
* For example, City of Nara 奈良 市 http://en.wikipedia.org/wiki/Nara,_Nara
(section 1 Etymology According to the most complete extant historical record of ancient Japan Nihon Shoki 日本書紀 [720 AD] the name "Nara" derived from the Japanese verb narasu 平す "to flatten")
, an ancient capital (710-784 AD) of Japan came from kanjis 奈 pronounced "na" and 良, "ra."
* Indeed, the hiragana and katakana of Japanese letter "na" is abbreviated from 奈
Na (kana) http://en.wikipedia.org/wiki/%E3%81%AA
, so are those of 良.
Ra (kana) http://en.wikipedia.org/wiki/%E3%82%89
(iii) hate 果て 【はて】 (n): "the end; the extremity; the limit"
Jim Breen's online Japanese dictionary