From my view (in the US), it seems mostly generational.
My grandfather William went by Bill, but most of the Williams in my own generation go by Will. In particular if they're the son of a Bill, they use the different nickname. I wonder if their sons will go back to Bill.
I've seen this alternate nickname scheme in a family that reused women's names down the line, with "Katherine" and "Elizabeth" taking turns and wearing nicknames left and right. Grandma was Katherine, grand-aunt was Eliza, mom was Kate, aunt was Beth, daughters were Kitty and Libby...
> I've seen this alternate nickname scheme in a family that reused women's names down the line
I've been doing a smidge of genealogy lately, and my dad's side of the family is full of this kind of stuff. They have a tradition of first son takes dad's dad's name, first daughter takes dad's mom's name, second son takes dad's uncle's name, etc. Not a lot of middle names. My great grandmother's maiden name is the exact same as her mother's married name, although some records have a shortened form, mostly for my GGM, but sometimes for my GM. For my kid, we tried to look around and pick a name that wasn't super common, but also not unique; I think we did well with the whole name, but there were three of his first name in kindergarten; thankfully with different last names, but the initial of their last names were sequential!
My grandfather William went by Bill, but most of the Williams in my own generation go by Will. In particular if they're the son of a Bill, they use the different nickname. I wonder if their sons will go back to Bill.
I've seen this alternate nickname scheme in a family that reused women's names down the line, with "Katherine" and "Elizabeth" taking turns and wearing nicknames left and right. Grandma was Katherine, grand-aunt was Eliza, mom was Kate, aunt was Beth, daughters were Kitty and Libby...