😄 A very Speranzian complaint. The difficulty is that the evidence is frustratingly thin. What the source explicitly tells us is only that:  Precianus was one of the Precii who had been adopted into another gens, and that he was a jurist, a friend of Cicero and Trebatius Testa, and known to Caesar. [GREXv2 | Word]  It does not identify the adoptive gens. [GREXv2 | Word] So we have the curious situation that:  the original family survives in the name (Precianus), the adoptive family has disappeared from the surviving notice.  From a Roman point of view, that is almost backwards. Adoption was normally meant to transfer a man into another house and perpetuate that house's identity. A Gricean might put it:  The implicature of adoption is: "This man's future belongs to the new family."  Yet in the surviving record the opposite has happened:  We remember that he was once a Precius. We do not know who adopted him. [GREXv2 | Word]  Hence your irony:  Speranza: What sort of Roman adoption is this? Grice: A very unsuccessful one. Speranza: The original gens survives in the name. Grice: And the adoptive gens vanishes from memory.  Exactly. As for Cicero, I would not say he ought to be embarrassed, but a historian certainly is! Cicero evidently thought his correspondents already knew perfectly well who Precianus was. The result is a familiar problem:  Contemporary writers omit precisely the information later historians most want.  For Cicero's audience the adoptive family may have been obvious. For us it is lost. So the most we can safely say is:  We know why he is called Precianus (because he had originally belonged to the gens Precia), but from the material before us we do not know the name of the gens that adopted him. [GREXv2 | Word]  Which is a splendid example of Roman onomastics defeating Roman genealogy.