It's very common, particularly for people who were born in the first half of the 1900s, to see that their first name was misspelled, or spelled differently to how their parents intended it, on the birth certificate. This occurs for a huge range of reasons. It's quite possible that your grandparents had a nurse fill in the birth certificate for them, and when they said "Elenore" (without spelling it out) the nurse wrote "Elinar".
Either way, it'll have the same derivation as Ellen / Elin, all the spellings of Eleanor, all of which are based on Helen.
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