The word “Assnarri” was used in the Second Century to ridicule African Gnostics who believed Christ was a form of Set or Seth. Set's Godhead was an ass or a jackal. This belief seems connectected with three African writers, St. Augustine, Tertullian and Apulieus. Tertullian and St. Augustine became Christians as adults. All were native to the same part of Madaurus in Carthage, Apuleius, a pagan is author of the wickedly clever "The Golden Ass". In addition to the grammarians Nonius and Maximus, St. Augustine, fifth century CE, studied there. Through a letter which he addressed later to the inhabitants whom he called “fathers”,we learn that many were still pagans.Thanks to the encouragement of Tertullian, Madaurus, had many martyrs who are known by their epitaphs; several are named in the Roman martyrology on 4 July. Three bishops are known: Antigonus, who attended the council of Carthage, 349; Placentius, the council of 407 and the Conference of 411;and Pudentius, sent into exile by Huneric with the other bishops who had been present at the Conference of 484.

In Pinning the Tale on the Donkey, Columbia University' s Richard W. Bulliet provides this information on the ass sex connection.

In two separate works written in the early third century, Tertullian relates this peculiar anecdote, which took place in Carthage. An apostate Jew and arena employee--one of those who allowed themselves to be mauled by wild animals--publicly paraded a picture of a man dressed in a toga and carrying a book, but with the head and distinctive ears of an ass. The hoof of an ass protruded from the toga. Beneath the picture was the following label: DEUS CHRISTIANORUM ONOCOETES (God of the Christians Onocoetes).
Astonishingly, Tertullian writes, "we laughed at both the label and the image" (risimus et nomen et formam). Not only did he find it funny to see the God he believed in so zealously depicted with a donkey's head; he also found the scandalous joke so memorable that he wrote about it twice.
The Belgian scholar Jean-G. Priaux, starts from the premise that the meaning of the unusual word must have been immediately apparent to Tertullian and other bystanders and within the plausible vocabulary of an arena lout. Comparing the word with vulgar sexual terms used by other authors of the period, he comes to the conclusion that the onlookers probably understood the label to be a play on the word embasicoetas, a synonym, more or less, for the words cinaedus and asellus. All three words refer to male prostitutes or libertines who offer their services to men and women. The special denotation of the unique term onocoetes, then, would have been a male prostitute equipped like a donkey, that is, with a thick penis over two feet long.
I hope this helps. ;)