DS is called a traditional name but very uncommon now. To say what it is would be to out me and it was in the 900s on the recent ONS list. It was more in use (though hardly very common) in the 40, 50s & 60s.
Would love to get similar ideas for DC2 (if it happens) ie mid-century but not used that often these days - definitely outside top 100.
I like for boys:
Teddy / Theodore - but am ruling out as too common
Peter
And for girls:
Margot
Gilda
Constance (likely to be a middle name)
Stella (too common now)