I know chazel say 40 days before the formation of a fetus a bas Kol goes out and says "bas ploni lploni" I was wondering in the language of the bas Kol, why does it say "bas ploni lploni" and not "bas ploni l ben ploni" or "ploni l plonis"?
The Ben Yehoyada (והנה מקשים) asks this and offers four answers:
The masculine is related to rachamim (compassion) and the feminine to din (severity). This enables evil forces to more easily attach themselves to a female. To avoid drawing negative attention to her, she isn't directly named.
Unlike the male, the female is initially under the control of her father, which is why only he can marry her off. Therefore she's identified with his name.
(Humorously) It's the girl's father who has to provide her wedding expenses and dowry, whereas the boy offers nothing from his side; if anything, he is also reliant on her dowry to set them up. Therefore her father gets the credit.
It wouldn't be appropriate for a heavenly voice to mention a female by name, so it uses her father's name.