I figured they would need a language, and rather than try and make up a native-sounding language, I found info on an ancient form of a language still spoken in the Americas today, though the modern form is very different from classical. I decided to use the classical form and have it influenced by English rather than Spanish, the language that influenced many of the real modern dialects of the language.
I also found info on several related languages and started comparing where they diverged. Interestingly, I found two languages spread further apart in modern times that were more closely associated before whites took over the US, so they often have similarities to each other for words that are completely different from the dead classical form of what I consider their mother language to the point that I have no idea how they got from the mother tongue to the modern ones.
However, it gave me a starting point to see how changes took place. I had derived a few words based on the mother tongue, and on comparing them with the real languages, I saw similarities in what I had derived with the real langs, but at the same time, the words were different, which is exactly what I was looking for; all three language groups should find many of the words familiar, while others will not be instantly recognized.
The writing system was actually much less of a challenge than I anticipated. Glyphs for the mother language are listed on ancientscripts.com, and taking a cue from the scribes of ancient Egypt, who came up with two faster ways to write their hieroglyphs, I studied the shapes of the language's known glyphs to come up with simpler forms to quickly print the derived language. Taking it one step further to a cursive form was much easier than I had anticipated, but I had had practice in taking an angular printed constructed script to a cursive form for a sci-fi book series.
It may sound like it took a long time to do all this for a couple of names, phrases, and descriptions in a book, but it only took a couple of lunch hours to accomplish, and as studying languages is a hobby of mine, they were pleasant hours.
