Proteus features one last small irruption of French (after sections focused on Patrice Egan, the Parisian follies, and Kevin Egan) when Stephen recalls Kevin "nodding for his nap."
"Alo! Bonjour" ("Hello! Good day!") appears to be Egan's friendly response as he looks up from his nap to see that Stephen has arrived. Both words are colloquial French greetings, though the first is usually spelled allo or allô.
From Kevin nodding off, Stephen's mind goes to another French nap—the faun's midday revery in Mallarmé's poem—and then back to his own stretched-out legs. Inside Mulligan's shoe is a "foot I dislove. But you were delighted when Esther Osvalt's shoe went on you: girl I knew in Paris. Tiens, quel petit pied!" The French means, "Look, what a small foot!"
From such a master of verisimilitude as Joyce proves himself in Ulysses, "girl I knew in Paris" is disconcerting. Would Stephen really explain to himself who Esther Osvalt was?