Ḥusn al-taʿlīl
Attributing a quality to a fitting, subtly imagined cause that is not its actual cause.
Here, “causal explanation” is a rhetorical device rather than an ordinary scientific or historical account. The poet assigns a delicate and appropriate imaginative cause to a state or quality. The invented cause enriches the intended meaning. Simply giving the actual cause of an event does not ordinarily constitute this figure.