There are various synonyms for the phrase "boastfully called" that you can use in your writing to add flavour and prevent repetition. Some of these synonyms include "proudly dubbed," "arrogantly named," "haughtily designated," "vainly titled," "self-importantly christened," "conceitedly identified," "egotistically labelled," and "swaggeringly denoted." These expressions convey an air of arrogance or vanity, suggesting a person or thing is defined by their own self-importance. Using synonyms like these when writing can help to make your work more interesting and engaging by conveying emotion and character.