According to "Shindaishi no shinkenkyu" (New study on History of the Times of Gods) written by Kurakichi SHIRATORI, published by Iwanami Shoten, Publishers in 1954, the name Izanagi is combination of words 'isa' derived from 'isao' meaning pious acts and 'gi' meaning a male.
「いさ」は「功徳」の意の「功（いさを）」の語根で、「き」は男性を表す語（白鳥庫吉『神代史の新研究』岩波書店1954年）。