Green’s Dictionary of Slang

my Prussian blue phr.

[SE Prussian blue, a colour; Dickensian use as synon. for SE true blue]

a term of endearment.

Show quotations
[UK]Dickens Pickwick Papers (1999) 432: ‘Vell, Sammy’, said the father. ‘Vell, my Prooshun Blue’, responded the son.
[Aus]Bell’s Life in Sydney 29 Jan. 3/1: Och, my Prussian Blue,’ exclaimed Biddy [...] ‘does your mother know you’re out?
R.H. Newell Orpheus C. Kerr I 19: All right, my prooshian blue, thinks I, there’ll be a ’pothecary’s bill for some family.