Mystery Monday- Bridget in Life, Elizabeth in Death

My great grandfather came to America in 1911 from Scotland with his mother and many siblings. One day his mother decided to pack up all the kids and leave her husband to venture to America...but that's another mystery. In any event, my great grandfather's paternal grandmother was Bridget Rafferty, born in Ireland circa 1818. She married Edward Campbell, also born in Ireland, circa 1808, and they eventually moved to Kilmarnock, Scotland. In 1857, Peter Campbell, father to my great grandfather, was born in his home on Strand Street in Kilmarnock, to Edward Campbell and Bridget Campbell, M.S. Rafferty, this according to his birth certificate.

On Peter's wedding certificate, dated 1884, he lists his parents as Edward Campbell, deceased, and Bridget Campbell, M.S. Rafferty, also deceased.

On Peter's sister's marriage certificate, she too lists her parents as Edward and Bridget.

On the 1861 Scottish Census the mother is listed as Bridget.

WHY then is Peter's mother listed as Elizabeth on her death certificate? There are no Elizabeths (nor Bridgets) in the naming pattern of the family, so no helpful clues there. The only way I knew this to be the right person (Bridget Campbell, MS Rafferty) is  because of the street address and husband's name. How could no one know she was Elizabeth?

I know, as is evidenced in much of my research, that people often use a middle name as their forename, but almost always others in the family know his/her given name and list so on their documents. Bridget's children did not, so did they know? I'm sure once I have made another breakthrough on this branch of the family, all answers will be obvious...or will they?

I invite you to share any insights you might have in the comments below.

*All records I mentioned above were accessed through Ancestry and ScotlandsPeople.