I believe it comes from Margreta which is like Margaret
Greta Ekman's birth name is Greta Sundstrm.
Greta Thyssen's birth name is Greta Thysegen.
Greta Stanton's birth name is Greta Wertheimer.
Greta Scacchi's birth name is Gracco, Greta.
Greta Muller's birth name is Greta Anne Muller.
Greta Gerwig's birth name is Greta Celeste Gerwig.
Greta Granstedt's birth name is Greta Irene Granstedt.
Greta Onieogou's birth name is Greta Adah Onieogou.
Greta Garbo's birth name is Greta Lovisa Gustafsson.
Greta Kline's birth name is Greta Simone Kline.
Greta Bjerke's birth name is Anna Greta Maria Bjerke.
Greta Cervantes's birth name is Greta Pamela Cervantes Gmez.