To many people on the internet, the actress Toni Collette is known simply as “mother.”Ms. Collette has played more than her share of mothers throughout her career: a matriarch with dissociative identity disorder on the TV show “United States of Tara”; a miniatures artist whose family is haunted after the death of her own mother in the film “Hereditary”; and, more recently, an American mom charged with taking over her Italian family’s mob business in the movie “Mafia Mamma.”But Ms. Collette is not necessarily called mother for playing fictional ones, or even for being a mother in real life. Instead, fans have bestowed the title as a way to express their appreciation. When fans call her mother, which they often do, “it feels like a well-intended, collective, familial, warm hug,” Ms. Collette said in an email. She is just one of the many female celebrities who, if lacking a proper understanding of the word’s new use, might wonder why they suddenly have so many children.

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