Regarding the doublets CEBU and SUBGU:

  Here is a “by the way” thought on the etymology of “Cebu” based upon Jason Lobel & Laura Anderson's wonderful article on a great number of newly identified Negrito languages submitted to OL.
  I have often wondered why Cebuanos via English call the city “Cebu” 
[seybu] when they clearly say [sugbu] when speaking in their mother 
tongue. Thanks to their paper and one by Pennoyer years ago, there were clearly PAN *R y languages in the central Philippines. There are 
several “irregular” odd reflexes in Palawano, Aklanon, Bikol, and many other dialects.
  I now believe that all of them are loans from original Negrito 
populations living throughout southern Luzon and the Bisayas (i.e., 
not just Pampango and North Mangyan, which regularly reflect *R>y).  
  At any rate, what do you think of this hypthesis?
  The aboriginal Negritos of Cebu Island called the area around Cebu City [seybu] < *seRbu "dip, dunk into liquid." When the Cebuanos came, they made a loan calque for that place name with their own cognate [sugbu], but keeping the original local word as a doublet [seybu].
  Just a thought. I would appreciate your comments tremendously.