Green’s Dictionary of Slang

smother v.

1. (UK Und.) to stand guard and cover for an accomplice breaking into a premises.

[US](con. 1910s) D. Mackenzie Hell’s Kitchen 123: One man ‘smothers’ (covers up – stands guard) while another puts the jemmy into the door or window and ‘knocks it off’.

2. (Aus. Und.) to use some form of object to obscure the shopkeeper’s view while a shoplifter abstracts a targeted object; also of a pickpocket.

[Aus]Bulletin (Sydney) 26 Apr. 45: Marg and Ratty Jack was gonna smother with a big box while Limp tugged the goose behind the counter. I was take man behind the box.

In exclamations

I’ll be smothered! (also you be smothered! I’ll be squashed!)

a general excl.

[UK] ‘Gallery of 140 Comicalities’ Bell’s Life in London 24 June 1/3: You be smothered, you old Brimstone!
[UK]J. Lindridge Sixteen-String Jack 83: I’ll be squashed if she didn’t give him the lovliest spat in the peepers that iver I saw in all my born or unborn days.
[Aus]Bell’s Life in Sydney 7 Apr. 3/2: ‘You be smothered!’ replied the saucy youth.
[Aus]Bell’s Life in Sydney 3 Dec. 2/7: Work be smothered, I’m a gentleman.
[UK](con. 1840s–50s) H. Mayhew London Labour and London Poor III 82/2: I’ll be smothered if I’m going to look down that gallows long chimney!
[UK]Boy’s Own Paper 24 Dec. 197: I’ll be smothered if they hain’t took me for a ghost!