This paper investigates the problem of adaptive fuzzy periodic event-triggered control for output-feedback interconnected switched nonlinear systems under arbitrary switching. Fuzzy logic systems are employed to approximate the unknown nonlinear terms. A state observer and fuzzy adaptive laws are constructed by using only the sampled output information. To reduce the waste of communication results, a novel controller is developed that only uses the information at the event-triggered instants. Furthermore, the proposed discrete-time event-triggering mechanism performs intermittent monitoring at the sampling instants. It is finally proven that all states of the closed-loop system remain bounded under arbitrary switching, and the effectiveness of the proposed scheme is verified through simulation results.