Pak Pak

Pak Pak, also known as Neimoidian, was the main language spoken/conveyed by the Neimoidians. Pak Pak was both a verbal and nonverbal way of Neimoidian communication.

Verbal Pak Pak
Verbal Pak Pak was the main, and possibly only, spoken Neimoidian tongue before the species began to learn and speak Galactic Basic Standard. It was noted that when an observer noticed two or more Neimoidians engaged Pak Pak, they heard a "chorus of staccato guttural croaks of infinite and subtle variety" that had a "certain musical beauty to it".

Originally, all Neimoidians used Pak Pak, but as the race began to expand across the Galaxy, the greedy Neimoidians realized that, in order to trade with other species, they needed to learn to speak more Basic.

The spoken Neimoidian language was based off of deep sounds produced by the throat of Neimoidians, and in order to speak this properly, the speaker would have to vary the shape of their throat cavity. Because of the difficulty non-Neimoidians had producing these sounds, the Neimoidians started to learn and speak Basic, although with a noticeable accent.

Still, Pak Pak was the dominant language on Neimoidia and the three Neimoidian purse worlds: Cato Neimoidia, Deko Neimoidia, and Koru Neimoidia.

This form of Pak Pak could have possibly been a form of the Duros language Durese, since the Neimoidians are in fact descendants of Duros.

Nonverbal Pak Pak
The main source of Nonverbal Pak Pak is unknown, but what was known of this form of the Neimoidian language was that it was conveyed through complex hand gestures.

Nonverbal Pak Pak was mainly used privately by those remaining isolated on their homeworld.

Behind the scenes
In the German version of the prequel trilogy, the Neimoidians were given French accents (and vice versa for the French version).
 * Although many have accused the Neimoidians' accent in Basic of sounding very familiar to certain Asian accents, especially Chinese ones, in the earthly language English, typical phonetic characteristics of Japanese or Chinese accents in English (e.g. rhotic [l] or lateral [r], dropped sounds in certain consonant clusters, or weakening of consonants closing syllables) are absent in Neimoidian speech, and characteristics of Thai, Vietnamese, or other accents are also not present. Thus, it is difficult to provide a cogent or concrete linguistic justification of this claim. The "mushmouthed" accent has been interpreted as stereotypically Chinese by some, despite the lack of concrete or specific characteristics of Chinese-accented English. Much of this may be due to the poor lip-syncing on the Neimoidian puppets used in The Phantom Menace, giving the impression of Japanese horror movies, as well as the horizontal slits found on Neimoidian eyes, similar to the slit-like eyes used in Asian caricatures, often deemed to be offensive.