Jenifer

This name could be the original Cornish spelling of Guinevere (also spelled as Gwenhwyfar in Welsh).
https://www.reddit.com/r/namenerds/comments/14wqmmt/lets_talk_about_jennifer/
https://www.cornwalls.co.uk/culture/cornish-names
https://www.houseofnames.com/jenifer-family-crest
https://www.behindthename.com/name/guinevere

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The variant 'Jennifer' only became more popular after the George Bernard Shaw's play The Doctor's Dilemma in 1906.
https://www.houseofnames.com/jennifer-family-crest
https://www.behindthename.com/name/jennifer

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Oh! And the variant of Jenefer should also be added!
https://www.behindthename.com/name/jenefer/submitted

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Thanks to @clevelandkentevans for pointing this out!

Also Czech: https://cs.m.wikipedia.org/wiki/Jennifer - listed as a variant

Also Portuguese:

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https://www.behindthename.com/name/jenifer/top/brazil
https://en.m.wiktionary.org/wiki/Jenifer#Portuguese

The name Jenifer was given to 74 baby girls born in the US in 2012.