Definition of "sniggered"
(British, obsolete, slang) Damned, in the sense of "I'll be damned if...", expressing utter certainty.
Quotations
I'm sniggered if I knows what it means.
1863, Elizabeth Caroline Grey, Good Society; Or, Contrasts of Character, page 52
I'm sniggered if this ain't a pretty job!
1886, George William M. Reynolds, The mysteries of the court of London, volume 8, page 174