The UK's biggest site for parents, and sister site, Gransnet, surveyed over 2000 parents and grandparents.
Nineteen per cent of grandparents said "they hate or have hated their grandchild's name".
Almost one in six (15 per cent) of parents say they have a parent or in-law who hates their child's name.
Six per cent have fallen out with them over the issue. Four per cent said the disagreement was so bad, "they have ended their relationship" with that person.
At the moment of the big reveal, 11 per cent of parents disbelieved their parents or in-laws when they claimed to love the baby's name.
Three per cent said their undiplomatic first response to the name was laughter, and 10 per cent said their initial response was: "What?"
The top reasons for grandparents' objections, according to parents, was the name being "too odd" (28 per cent) or annoyance their suggested name had not been used (20 per cent).
Other objections included the name being "made up" or "unconventional" (15 per cent) or "too old fashioned" (11 per cent).
There were also concerns the name would "embarrass the child"; it reminded a grandparent of someone they disliked or they were annoyed a family name had not been used (all ranked 10 per cent).
But some simply thought the name was "too plain or ugly" (5 per cent); too hard to pronounce (4 per cent) or too difficult to spell (3 per cent).
Grandmothers have much stronger views than grandfathers, according to the research.
Forty-four per cent of parents who reported objections said the complaints came from their own mother and 42 per cent cited mothers-in-law.
Just 14 per cent said the criticism came from their own father, and a further 14 per cent from fathers-in-law.
In an attempt to get around using the "hated" name, parents say that 9 per cent of grandparents avoid using it at all.
A further 9 per cent insist on calling the child by a shorter version of their actual name.
Mumsnet founder Justine Roberts said "Choosing a baby name is fraught enough for parents if you're only taking into account your own views; if you add grandparents' biases to the mix it can become impossible, unless by some freakish chance you're all in agreement that the baby has Cedric written all over him.
"Parenthood is one long object lesson in not pleasing everyone, and new parents should think of any naming tussles as preparation for coming battles over what constitutes an appropriate outdoor outfit, whether it's all right to cut the cat's hair, and whether two hours is enough time to revise for a GCSE."
The most unpopular names
• Aurora
• Charlotte
• Edna
• Lindsay
• Sally
• Bertha
• Tabitha
• Jack
• Noah
• Roger
• Elijah
• Frank
• Finn
• Ian