Green’s Dictionary of Slang

1. a blow to the throat.

1825		Pierce Egan’s Life in London 9 Oct. 301/1: Gybletts planted a tremendous throttler — a sort of choker, which floored Robin.
1847		Bell’s Life in Sydney 10 Apr. 2/5: After receiving a throttler, Hough stooped, as if going down.
1855		(con. 1821) Fights for the Championship 65: Neat endeavoured to administer another left-handed throttler.

2. a necktie.

1961

(con. 1920s) J. Sparks Burglar to the Nobility 8: A proper dandy bloke who sported [...] a lavender satin throttler with a diamond prop-pin in it.