Specifically, the fear of mother in law is Pentheraphobia. The origin of the phrase penthera is Greek (meaning mother-in-law) and phobia is Greek (meaning fear). It is also known as Novercaphobia.
Pentheraphobia is considered to be a particular phobia. People with this phobia may additionally have issues with Vitricophobia (fear of your step-father) Novercaphobia (fear of your step-mother), and Soceraphobia (fear of your parents-in-law).
The symptoms for this phobia can include: anxiety, a feeling of dread, shortness of breath, sweating, dry mouth, nausea, irregular heartbeats.
Pentheraphobia may be the result of false expectations with relation to your in-law. And individual might think that all moms are the same and that the new in-law will be cut from the same cloth as their own mom, but this is rarely the case.
Interestingly it may be the mother-in-law that has the best opportunity to lessen the fear. One ritual that can help right from the start is to have the husband’s mother offer her new daughter-in-law or son-in-law an apron with the strings cut. This symbolizes the mother-in-law’s wish to demonstrate her intentions to remain hands off in her child’s new marriage.
The other relief from this phobia is to seek help and sometimes intervention with a therapist who can help you learn ways to manage your fear and skills to establish your own home apart from the undue influence of your mother-in-law.