Nursery Rhyme Backstory: Jack and Jill

Seven daughters and a son
had Captain Basil Brassington.
His heir apparent Jack was named;
some seven sisters Jack proclaim'd.
     First, Sydney (short for 'Saint-Denys'),
then Signe (means 'new victory'),
then Sigrid and Simone, the twins 
(call'd 'Sig 'n' Simo' for their sins).
     Then Silvie and Sigourney (whom

you've seen on TV, I presume),

and, last (nor least) the baby, Jill,

who, with her brother, climb'd that hill.