Green’s Dictionary of Slang

scragger n.

a hangman.

1897		‘Price Warung’ Tales of the Old Regime 213: We’re all a-stuffed in ’ere till the scragger comes along for you fellows.
1905		Sun. Times (Perth) 26 Nov. 4/8: ‘The Suspension of Billington’ was the heading of one of the cables that appeared in this week's dailies. As a gentleman of that name is (or was) official scragger in the old country, the item seemed sufficiently sensational to merit closer attention.