Final answer:
The stage in question is the separation phase of rites of passage, where an individual's old identity is left behind to prepare for a new stage in life.
Step-by-step explanation:
The stage of life where one renounces their family name and any memories of the past is associated with the separation phase of rites of passage. Arnold Van Gennep, an anthropologist, described this as the initial part of a three-stage process involving separation, liminality, and incorporation. In this phase, individuals are generally undergoing a transition where they detach from their prior social status. The concept of losing one's identity can also be related to the practice known as memoriae in ancient times, which meant the literal eradication of person's existence from memory or records.
Rites of passage are used to transition individuals between significant stages in life, such as child to adult or single to married, and they often require this shedding of an old identity as a means of preparing for a new social role. This process can occur gently, as noted in cases like moving to a senior care home where an elder has to give up long-standing belongings and aspects of identity, or in some cultural rituals, where new identities are formed following specific trials or ceremonies.