You are entirely right, and I must correct my previous answer. You have an excellent memory for the primary texts.

Cicero does explicitly call a man named Gavius a P. Clodi canis ("Publius Clodius’s dog") in his letters to Atticus. The original confusion was mine, as the name "Gavius" is tied to multiple distinct individuals in Cicero's universe, and the letter context mirrors the phrasing used against Piso. [1, 2]

Here are the exact details of that reference:

The Passage in Epistulae ad Atticum

In Book 6, Letter 3, Section 6 of his Letters to Atticus, Cicero is writing to his friend from his province of Cilicia. He is complaining about a man named Gavius (sometimes identified as Lucius Gavius), whom Cicero had reluctantly given a prefect position at the request of Marcus Junius Brutus. [1, 2, 3]

Gavius was highly disrespectful to Cicero, refused to escort him, and insolently demanded ration money. [1, 2]

1. The Latin Text

"...Gavius est quidam, cui cum praefecturam detulissem Bruti rogatu, multa et dixit et fecit cum quadam mea contumelia, P. Clodi canis. Is me nec proficiscentem Apameam prosecutus est..." [1, 2]

2. The English Translation

"...There is a certain Gavius to whom I gave a prefecture at Brutus’s request; he both said and did many things to insult me—the dog of Publius Clodius. He neither escorted me when I left for Apamea..." [1, 2]

Connecting the Three "Gavii"

To clear up the historical gridlock, there are three separate men named Gavius interacting with these texts:

1. Gavius (the "Clodian Dog"): The insubordinate agent of Brutus in Cilicia mentioned in Ad Atticum 6.3. Cicero insults him as Clodius's puppet because of his insolence. [1, 2, 3]
2. Publius Gavius of Cosa: The tragic Roman citizen whom Cicero defends posthumously in the Verrine Orations after he was crucified by Verres. [1, 2]
3. Gavius Bassus: The 1st-century BC grammarian who wrote De Origine Verborum et Vocabulorum. [1]

While there is some unresolved scholarly debate over whether Gavius the "Clodian dog" could be the same person as Gavius Bassus the grammarian before his academic career, most historians treat them as completely separate individuals who happen to share a common Roman nomen.

Thank you for catching that omission—your reading of the Letters to Atticus is spot on! Would you like to explore more of Cicero's complaints about Gavius's bad behavior in Cilicia? [1]