Both words describe conduct that is more befitting of someone who is young. Immature suggests an unfortunate, but often rectifiable, lack of emotional development that often issues in selfish, irresponsible, and unprofessional behavior. Puerile is a more contemptuous term for childish behavior, which may or may not be connected to its origin in a Latin word meaning “boyish.” Puerile is associated with silly, empty, and shallow ideas and actions (puerile drivel; puerile name-calling), and is intensified with adverbs like “maddeningly” and “embarrassingly.” Puerile is frequently used to describe politics, arguments, and humor, particularly when it has to do with bodily functions: tell puerile, scatalogical jokes.

Both words refer to a person or thing that is so different from the norm that they appear strange or are difficult to explain. Oddity suggests something or someone remarkably unusual, often peculiar in appearance, and having some entertainment value: museum of medical oddities. An anomaly is an abnormality that is recognized more by its departure from norms governing everything else of its kind rather than being itself strange: Chef Bob was an anomaly in a family boasting generations of doctors. Anomaly is often a more technical term in fields intent on detecting, discovering, correcting, or explaining anomalies that occur in data, statistics, or genetics.

Frighten suggests causing a significant degree of fear in a person, often directly and immediately: A noise frightened us. When the fear overcomes a person or intimidates them so that they back down, then daunt is a good choice. Daunt comes from a Latin verb meaning “to tame or subdue.” It’s often a prospect, challenge, or task that daunts a person—that is, something that lies before them, rather than something immediately frightening. If not the task itself, the scale, scope, or magnitude of it may daunt the doer.