Ana Aquiningoc Sablan (Berete) Iriarte
with her daughter Matilde
and grandchildren Francisco and Catalina
A branch of the Sablans are called familian Berete.
In my experience, Chamorro nicknames usually come in only two categories : the easily explained and the totally puzzling.
Examples of the easy ones are known Chamorro words like familian Chunge' (white haired) and familian Gualåfon (full moon). Some nicknames come from the first names of ancestors like familian Kaila (Micaela) and familian Sinda (Reducinda). Once you see the names of ancestors in these families, it isn't hard to see where the nickname comes from.
Still other families have nicknames derived from a surname associated with the family. The familian Kottes are so-known because at one time their middle name was Cortes (Cortes Torres) and another branch of the Torres are called Agilat because their middle name at one time was Aguilar (Aguilar Torres).
Then there are families whose nicknames come from Spanish words. So, if you are familiar with Spanish, you will understand the nickname rather easily. The familian Seboyas are named after onions (cebolla in Spanish) and the familian Katson are named after trousers (calzón in Spanish). You need to know some basic rules about how Chamorros modify the original Spanish pronunciation to get this, though.
When a Chamorro family nickname includes a letter that is not favored by the Chamorro language, such as the R in Berete, a good guess is that the name is foreign, that is, not Chamorro in origin. That means there's a good chance the foreign word is Spanish.
Some Spanish words are so obscure, though, that these nicknames take a while to decipher. One such example is Kueto. There is a Spanish last name Cueto, but, as far as we can tell, no Taitano was ever married to someone with the last name Cueto. Then, family oral tradition comes to the rescue, as it did with Kueto, because Carlos Taitano, a Kueto, told me that his family got this nickname because his grandfather liked a Spanish song whose title included the word Cueto. He heard this explanation from his elders.
If you exhaust all the Spanish dictionaries and never find the word you think might be Spanish, it sometimes pays to look up the word in dictionaries of other languages spoken in Spain.
One of these other languages is Galician (or Gallego). It is spoken in Galicia, a province in the northwest corner of Spain. Their language is somewhat similar to Portuguese.
This red-colored portion of Spain is called Galicia
Now keep in mind that this is only a guess, but a guess with some backing. Many Chamorros knew many Spanish words, even words that were not common in most of Spain. There were some Spaniards from Galicia who lived on Guam, like some missionary priests. We even got our word for the farmer's hoe, the fusiños, from the Galician language of Spain, not the Spanish (or Castilian) language.
It is entirely possible that some Chamorro was given a nickname based on a Galician word for this fish. Why? That's almost impossible to answer, unless someone in the family heard the story from long ago.
But since we have no solid proof that the Berete family is so-named because of this Galician name for this kind of fish, we have to leave room for other possible explanations.