Iolanthe

... is a fairy, who has been banished from fairyland because she married a mortal. This is forbidden by fairy law. Her son, Strephon, is an Arcadian shepherd who wants to marry Phyllis, a Ward of Chancery. All the members of the House of Peers also want to marry Phyllis. When Phyllis sees Strephon hugging a young woman (not knowing that it is his mother – immortal fairies all appear young), she assumes the worst and sets off a climactic confrontation between the peers and the fairies. The opera satirises many aspects of British government, law and society.

Dictionary.com defines 'peri' as "one of a large group of beautiful, fairylike beings of Persian mythology, represented as descended from fallen angels and excluded from paradise until their penance is accomplished", or "any lovely, graceful person".