There is an unsettled debate whether the sound made by the letter R belonged to the language of our ancestors before the Europeans came to our islands or not.
In other words, did our ancestors have the R sound in their language?
The doubt comes from the fact that Chamorro as we speak it today (and for some centuries now) lacks words that begin with R. Every Chamorro word that begins with R is a foreign word; mainly Spanish (riko, rifa, rai, rosåt) but also Japanese (rakkio') and English (redio).
When R appears at the end of a word, the word or name is foreign and we change it to a T. Spanish colar becomes Chamorro kollat (fence). The Spanish name Javier becomes Habiet in Chamorro.
When R appears inside a word, it changes to either an L or a T. Carlos and Ricardo become Kåtlos and Rikåtdo.
Spanish guitarra becomes Chamorro gitåla (guitar); alambre becomes Chamorro alåmle (wire).
Spanish barba becomes Chamorro båtbas (beard); determina becomes Chamorro detetmina (determine).
Why does the R sound appear unchanged in a few Chamorro place names and some words?
When our indigenous place names were written by the Spaniards using an R, in almost all cases, the people did not pronounce the R but used an L instead. Inalåhan, not Inarajan. Malesso', not Merizo. The same with Ritidian (Litekyan), Taragui (Talågi).
But then why does everyone, including older people, pronounce Orote with the R? And Urunao with the R? Is it possible that at one time people did say Olote? And Ulunao? When I say Talågi, older Chamorros do not look at me strangely. But when I once experimented saying Ulunao, even the older Chamorros owning land in Urunao looked at me strangely.
Besides place names, the word Chamorro is always pronounced with the R. Some would argue that the word Chamorro is not indigenous. Thus, R is used and pronounced.
Chamorros did not always replace the Spanish R with a Chamorro L. Riko is always riko; karera is always karera.
Some Chamorros did have a problem with the R sound even when most over Chamorros did not.
I remember an older lady, now deceased, telling me how some people could not say Santa Cruz, the district of Hagåtña west of San Ignacio district where the Plaza is. Instead, they would say Santa Klus.
And in the video below, the lady says para using an L instead of the R, two times and once with an R.
So, in summary we can say that, although not in a consistent way, Chamorros have a hard time with the R sound and tend to replace the R on many occasions. The unsolved mystery is whether Chamorros always had this difficulty or did they in fact pronounce the R sound in days past.