The name papilionatae and cruciferae is …

Both of the families Papillionaceae and Cruciferae are named in this way due to the characteristics of their corolla. The corolla or the petals are the portions of the plant that is present behind the calyx of the plant. This whorl is usually colored.
Papilionaceae: Another name for this family is Fabaceae. This is the pea family. The corolla of this family resembles a butterfly because of its arrangement. The name ‘papilio’ is Latin for butterfly. Therefore the name of the family is based on the shape of the corolla.
Cruciferae: Cruciform refers to a shape that is like a cross. This is the cabbage family. The flowers of this family all have four flowers that are positioned in a cross-like formation. The petals are positioned at right angles to each other which is what gives them this shape.