Deliana's used in Dutch as a form of Delia
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Deliana would be, approximately, , or , the place in Greece. Your spelling looks originally French, or perhaps Belgian.
When the swampy fen lands in the east of England were being drained - can't remember when, but certainly centuries ago - they imported experts and experienced workmen from the Netherlands, just across the Channel. So there was a strong Dutch influence for a while. And in East Anglia there are records of girls being named Dillian - presumably an Anglo version, combined with memories of Gillian