Reference: Fataawa Noor ‘alad-Darb – Question No.6473, Page 299, Volume 12
Question: Is calling the mother by her name considered as [being] disobedient to her? And [what] if I have become used to this, and she is fine with that – so would this be permissible?
Response: It is permissible for a person to call both his parents – or either of them by their name. However, it is not from good manners to do that, and instead it should be said [something like] ‘O my mother, [and] O my father’. And if he were to also include their name, then there is no harm is this, such as him saying ‘O my father fulaan, [and] O my mother fulaanah’. As for calling them by their names – without mentioning their parental title of ‘father’ or ‘mother’, then this is considered contrary to good manners [towards them].