I’ve been noticing that there are several English short forms / nicknames that used to be short for one name, but then became associated with a different full name — to the point where the connection to the original name has fallen out of use.
Quite often, the second full name wasn’t previously common, and it’s popularity was helped by the existence of a popular nickname.
Some examples:
Jenny (
Jane —
Jennifer)
Patty /
Patsy (
Martha /
Matilda —
Patricia)
Tess (
Esther —
Theresa)
Cassie (
Catherine —
Cassandra)
Addy (
Adam —
Adelaide,
Adeline etc)
Hank (
Hankin —
Henry)
Jem (
James —
Jeremy)
and maybe
Hal (
Henry —
Harold)
Ted (
Edward —
Theodore)
Can you think of more?