Green’s Dictionary of Slang

1. (Aus., also bag of flower) a girlfriend [rhy. unknown].

1914		Sport (Adelaide) 7 Mar. 5/4: What does it cost Barney F. to keep the bag of flower in cigarettes.
1914		Sport (Adelaide) 7 Mar. 5/4: You’ll have to save a little longer to buy cigarettes for your bag of flour.

2. a shower (bathroom, or rain).

1980		cited in Partridge DSUE (1984).
1992		R. Puxley Cockney Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.