From conversations with Lord Greystoke and from his notes, there have been gleaned a number of interesting items relative to the language and customs of the inhabitants of Pal-ul-don that are not brought out in the story. For the benefit of those who may care to delve into the derivation of the proper names used in the text, and thus obtain some slight insight into the language of the race, there is appended an incomplete glossary taken from some of Lord Greystoke's notes.

A point of particular interest hinges upon the fact that the names of all male hairless pithecanthropi begin with a consonant, have an even number of syllables, and end with a consonant, while the names of the females of the same species begin with a vowel, have an odd number of syllables, and end with a vowel. On the contrary, the names of the male hairy black pithecanthropi while having an even number of syllables begin with a vowel and end with a consonant; while the females of this species have an odd number of syllables in their names which begin always with a consonant and end with a vowel.

--Edgar Rice Burroughs,
Tarzan The Terrible