Speakers of many Trans New Guinea or Papuan languages use a number of reciproca person-referring expressions. Various examples are found in the Papuan language of Koromu, spoken in Madang Province, Papua New Guinea. This paper examines the meanings of Koromu reciprocal expressions that recall shared past experiences, in particular, social category terms connected with coming of age events and spontaneous nicknames created at the time events occur in the course of everyday life. The meanings are explicated in clear simple terms using Natural Semantic Metalanguage primes. The explications point to important aspects of social cognition, including identification with significant others based on shared experience and relational concepts of personhood. Although this study points to the possibility of some language endangerment for some meanings, it also indicates the ongoing cultural importance of shared experiences, including commensality, in both rites of passage and everyday life.