Many studies on software development have made it clear that naming identifiers consistently and concisely is challenging. Verification of software using consistency seems possible by ensuring that each name refers to only one concept throughout the entire software development. This should be based on naming concepts in the application domain, not the implementation domain. This paper presents a case study on the naming of identifiers in the description of software application domains, specifically in requirements analysis and specifications. The case study evaluated the similarity of the textual information of the identifier names in requirements analysis and the specifications, and analyzed the reasons for the lack of consistency from the answers to questions asked to the designers. The results show that the lack of consistency arises from the recognition of data structures and response to changes in the external environment.