Echoing that this can be used as a nickname for Cassandra/Kassandra, in fact from what I've seen it's the most common full name for Sandra in English, that may just be confirmation bias though.Just like Cassandra, which can be said kuh-SAN-druh or kuh-SAHN-druh, this name can be pronounced SAN-druh or SAHN-druh. I've known two that use the latter pronunciation (one short for Cassandra one as a given name) and one pronounced SAN-druh (short for Cassandra).
In 2018, 63 is the most common age for an American (U.S.) Sandra who is registered female with the Social Security Administration. It is the 45th most common female first name for living U.S. citizens.
Sandra is also a Polish name. As for now I guess it's used more often as a name on its own than a diminutive of Aleksandra, because the most common nickname that almost every single Aleksandra goes by is Ola. Sandra became popular sometime between 70s-80s and is still fairly popular. It can be of course also a diminutive of Kasandra, but Kasandra isn't particularly popular. Sandra can be nicknamed to Sandi, Sandrusia or Sandrunia for instance. Pronounced SAHND-rah.
― Anonymous User 1/12/2018
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The name Sandra was given to 318 girls born in the US in 2016. More than 99.9 percent of people with the first name Sandra are female.
My mom's name is Sandra. She was born in Colombia. I don't know how my grandmother thought of naming her since Sandra isn't really a Spanish name. People call her Sandy sometimes.
It flourished in the USA between the last 50s and the first 60s due to actress Sandra Dee (b. 1942). Among others, Sandra's usage is also Czech, Polish and Swedish. In Hungarian it is written Szandra.
Just like Cassandra, which can be said kuh-SAN-druh or kuh-SAHN-druh, this name can be pronounced SAN-druh or SAHN-druh. I've known two that use the latter pronunciation (one short for Cassandra one as a given name) and one pronounced SAN-druh (short for Cassandra).