Green’s Dictionary of Slang

1. (Aus. und.) one who deliberately jostles and knocks over their victim so as to pick their pocket [? same as sense 3].

1895

Crowe Aus. Sl. Dict. 29: Trippers, or Rampers, robbers who cause people to slip on the streets and then rob them.

2. (Aus.) a foot.

1904

Sydney Sportsman (Surry Hills, NSW) 25 May 3/3: [S]omething smart and extra special in high heels and patent-leather on her trippers.

3. (UK und.) a female pickpocket.

1935

Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 11: Tripper: Female pickpocket.