Green’s Dictionary of Slang

1. the gallows.

1818

W. Scott Heart of Mid-Lothian (1883) 239: I think Handie Dandie and I may queer the stifler for all that is come and gone.

2. a dram of spirits.

1821

‘A Real Paddy’ Real Life in Ireland 125: A drop was melted down into the leaden cup, and all round took a stifler.

3. a severe blow.

1890–1904

Farmer & Henley Sl. and Its Analogues.