Wide island or south island
Syndey is a rare spelling variant of Sydney. It is derived from the Old English words 'sid' meaning wide and 'eg' meaning island, or potentially from the French Saint-Denis. While the 'Sydney' spelling is standard, this transposition of the 'd' and 'n' is occasionally used as a unique alternative.
Less common today
Syndey isn't in the latest US Top 1000. It last peaked at #4,186 in 2001.
US births per 5-year period, 1990βpresent (SSA data).