In the dark comedy Nightbitch, the main character is simply known as Mother, and though this distinction may seem innocuous, it actually hints at a much larger truth about the character. Based on a novel by Rachel Yoder, Nightbitch follows Mother, a woman who is the mom of a toddler, and as a result, feels as though her old self is slipping away. When Mother discovers that some strange changes are occurring to her body, she decides to embrace her new dog-like features in order to regain her sense of identity.

https://screenrant.com/nightbitch-amy-adams-mother-character-name-reason/