Usimbalda is a name I can’t seem to find the etymology for, but my educated guess is that it might be an Italian feminine form of the Ancient Celtic name Cunobelinus. Most people are more familiar with the feminine form of the name as Cymbeline, though of course, Decameron author Giovanni Boccaccio predated Shakespeare by several centuries. Then again, Usimbalda could have a completely different etymology.
Abbess Usimbalda appears in the second story of the ninth day of The Decameron, one of numerous people of the cloth violating their vow of chastity in these 100 stories. The Abbess is in bed with a priest when some of her nuns come running to tell her they caught Sister Isabetta in bed with a man. Usimbalda has frequently had her priest brought into her bedroom in a chest, and is terrified he might be discovered because her nuns are beating on the door so violently.
In her haste and in the dark, Usimbalda mistakes the priest’s trousers for her psalters (a type of veil), and goes off to catch the guilty party. Isabetta is dragged off to the convent’s meeting hall, and Abbess Usimbalda excoriates her. During this tongue-lashing, Isabetta sees the trousers on the Mother Superior’s head, and repeatedly tells her to tie up her wimple before saying anything more. The other nuns then notice it too, and Usimbalda realises she’s busted. She then begins to talk much more sweetly, saying no one can resist the temptations of the flesh, but that it must be done discreetly.
Ughetto may possibly be a diminutive of Ugo, the Italian form of Hugo/Hugh, a Germanic name meaning “mind/spirit/heart.” He appears in the third story of the fourth day, whose theme is love stories which ended tragically.
N’Arnald Civada, a wealthy Marseille merchant of humble origins, has three daughters, 15-year-old twins Ninetta and Magdalena, and 14-year-old Bertella. Their arranged marriages have been delayed because N’Arnald is away on business, and in the interim, a young, poor nobleman named Restagnone falls in love with Ninetta. Restagnone has two wealthy friends, Ughetto and Folco, who fall in love with the other two sisters.
Restagnone schemes to get rich through them, and convinces them to go with the ladies to Crete. They live like royalty in Crete, but eventually Restagnone bores of Ninetta, and sets his sights on another woman. Ninetta’s depression turns to fury, and she poisons Restagnone. She’s discovered as a murderer and arrested, and later Ughetto and Folco are detained overnight by police, as a pretext for the Duke of Crete to secretly spend the night with Magdalena.
Ninetta has been released in exchange for this night with her sister, but Ughetto and Folco have been led to believe she was tied in a sack and thrown in the sea. While they’re trying to console their wives for the believed loss of their sister, Folco discovers Ninetta and refuses to believe Magdalena’s story. (It wasn’t previously stated which of the other two men marries which of the other sisters, but this makes it obvious Folco has married Magdalena, and thus Ughetto has married Bertella.) Folco is so furious over her adultery, he stabs Magdalena with his sword. He then flees with Ninetta.
The next morning, the murder is discovered, and the Duke of Crete has Ughetto and Bertella arrested. He forces them to make a false confession about how they, not just Folco, murdered Magdalena. Fearing for their lives, they escape by ship to Rhodes at night, living the rest of their short lives in poverty and misery.