Given Nigeria’s societal norms and prevailing religiosity, topics of sex and genitalia are often regarded as taboo. Consequently, university students adapt their language to avoid being perceived as vulgar. This study investigates semantic shifts in sex and sex-related slang expressions among university students at the University of Nigeria, Nsukka, focusing on how such slang terms evolve to mask vulgarity. Qualitative data were obtained from forty undergraduates who were sampled using purposive and snowball techniques. Semi-structured interviews and a wordlist of sex discourse terms were used as methods of data collection. Drawing on Lakoff and Johnson’s Conceptual Metaphor Theory (CMT), this study reveals how metaphorical mappings are used in the transformation and concealment of sex and sex-related topics. The findings show that the students map the refined slang from domains in their environments to align with peers who share similar attitudes, and differentiate themselves from those who uphold religious and pious values. This study contributes to language shift by revealing how the refinement of sex-related terms facilitates lexical innovation, thereby promoting creativity in linguistic spaces that have religious and cultural barriers to the use of sex and sex-related expressions.