Clodius is an alternate form of the Roman nomen Claudius, a patrician gens that was traditionally regarded as Sabine in origin. The alternation of o and au is characteristic of the Sabine dialect. The feminine form is Clodia.
During the Late Republic, the spelling Clodius is most prominently associated with Publius Clodius Pulcher, a popularist politician who gave up his patrician status through adoption in order to qualify for the office of tribune of the plebs. Clodius positioned himself as a champion of the urban plebs, supporting free grain for the poor and the right of association in guilds (collegia); because of this individual's ideology, Clodius has often been taken as a more "plebeian" spelling and a gesture of political solidarity. Clodius's two elder brothers, the Appius Claudius Pulcher who was consul in 54 BC and the C. Claudius Pulcher who was praetor in 56 BC, conducted more conventional political careers and are referred to in contemporary sources with the traditional spelling.
The view that Clodius represents a plebeian or politicized form has been questioned by Clodius's chief modern-era biographer. In The Patrician Tribune, W. Jeffrey Tatum points out that the spelling is also associated with Clodius's sisters and that "the political explanation … is almost certainly wrong." A plebeian branch of the gens, the Claudii Marcelli, retained the supposedly patrician spelling, while there is some inscriptional evidence that the -o- form may also have been used on occasion by close male relatives of the "patrician tribune" Clodius. Tatum argues that the use of -o- by the "chic" Clodia Metelli was a fashionable affectation, and that Clodius, whose perhaps inordinately loving relationship with his sister was the subject of much gossip and insinuation, was imitating his stylish sibling. The linguistic variation of o for au was characteristic of the Umbrian language, of which Sabine was a branch. Forms using o were considered archaic or rustic in the 50s BC, and the use of Clodius would have been either a whimsical gesture of pastoral fantasy, or a trendy assertion of antiquarian authenticity.