The term 'cause of worry' can be defined as something that causes anxiety or fear. This term can be expressed in a variety of ways, such as PERIL (5 letters), BUGABOO (7 letters), HEADACHE (8 letters), and ANGST (5 letters). PERIL is a state of danger or risk, while BUGABOO is an object of dread or fear. HEADACHE is a physical pain in the head, and ANGST is a feeling of deep anxiety or dread. All of these terms can be used to describe a cause of worry.