Green’s Dictionary of Slang

miller’s daughter n.

[rhy. sl.]

water.

[Scot]Eve. Teleg. (Dundee) 3 Aug. 4/1: 'Pass me the miller' refers to the 'miller's daughter,' and signifies water.
[UK](con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier.