Zinevra seems like an old Italian form of Genevra, a name which also appears in The Decameron as Ginevra (sixth story of the tenth day). It’s the Italian form of Guinevere, which is combined from the elements “fair, white” (gwen) and “smooth” (hwyfar). It may also be related to the Italian word ginepro, “juniper.”
Zinevra appears in the ninth story of the second day, as the unfairly accused wife of the foolish Bernabò da Genoa. Bernabò agrees to a ridiculous bet with his so-called friend Ambruogiuolo da Piacenza, and loses all his money when Ambruogiuolo tricks him into believing Zinevra has been unfaithful. Ambruogiuolo creeps into Zinevra’s bedroom when she’s sleeping naked, and finds a mole under her left breast, with six soft golden hairs around it. He takes some of Zinevra’s belongings before sneaking off.
Bernabò really was setting himself up to be a victim, the way he was so overly trusting of Ambruogiuolo and insistent about Zinevra’s absolute loyalty. Full of shame over losing his money and hearing the lie about Zinevra’s unfaithfulness, he orders a servant to murder her. The servant has pity on Zinevra and leaves her to escape with his clothes. Eventually, Zinevra finds her way to Alexandria and enters the service of the Sultan, under the male identity Sicurano da Finale.
Ambruogiuolo later comes to the city and makes friends with Sicurano/Zinevra, and she finally discovers just why Bernabò was so angry at her. She arranges for her poverty-stricken husband to come to Alexandria, and in the presence of the Sultan, Bernabò, and Ambruogiuolo, she reveals herself as a woman and exposes Ambruogiuolo as the liar and scoundrel he is. A very macabre just desserts are meted out, and the story closes with the awesome line, “And thus it was that the deceiver lay at the mercy of the deceived.”
Zima appears to be derived from Simon, whose original form is the Hebrew Shimon and which means “he has heard.” Though the word zima means “winter” in the Slavic languages, it doesn’t seem likely an Italian name in the Middle Ages would be derived from a Slavic root. However, in The Decameron, Zima’s real name is Ricciardo, with a nickname derived from azzimato, “ornately dressed; decked out in one’s best clothes.”
Zima appears in the fifth story of the third day, as he lusts after the wife of Messer Francesco Vergellesi, a knight of Pistoia. He’s unsuccessfully been courting the lady for quite some time, until one day he agrees to sell Francesco his prize horse from Tuscany. Zima only agrees to part with this precious horse on condition he be allowed some words with Francesco’s wife in Francesco’s presence. They’re sitting far enough away from Francesco to not be overheard, and though the lady doesn’t say a word, Zima sees a certain glint in her eyes and speaks what he believes is on her mind, as though she’s the one speaking.
Francesco is soon going to Milan to serve as podestà, and Zima tells the lady of a sign to let him know when the house will be empty. Once Francesco is gone, believing he’s got a true-blue wife, the lady realises Zima can sexually satisfy her far more than her husband, who won’t be back for a good six months. They finally become lovers, and even after Francesco returns, they continue discreetly enjoying themselves.