wheel of fortune
Trollope is invoking the Latin phrase rota fortunae, “wheel of fortune,” which indicates a Classical mode of thought about the way in which fortune operates. Reginald is made squire “by a turn in the wheel of fortune.” The Roman playwright Pacuvius wrote of the goddess Fortuna as standing on a ball blindly falling in any direction. In this way, Fortuna is unconcerned about the well-being of humans and is inconsistent in her allotment of good or bad. [CD 2012]
Fragment of Pacuvius quoted in the Rhetorica ad Herennium 2.23.36.