Green’s Dictionary of Slang

absent-minded beggar n.

a soldier.

1899		Manchester Courier 19 Dec. 8/4: In reply to a lady [...] asking for a definition of the term ‘Absent-minded Beggar’ [...] Mr Rudyard Kipling desires me to say [...] the term [...] is one used by private soldiers when they have forgotten any small durty and ‘beggar’ is a generic term of endearment.
1900		Bulletin (Sydney) 13 Jan. 11/1: Kruger is at the top, and his facial expression is supposed to become more and more wild as the Absent-minded Beggar comes nearer. Owing to certain recent slippings-down of the Beggar, however, Kruger’s face-barometer kept set fair.
1900		Blackburn Jrnl 4 Aug. 9/2: An Absent Minded Beggar. [...] An interesting instance of the absent-mindeedness of the ‘gentleman in khaki’. He had mistaken his lodgings.
1905		Lancs Eve. Post 1 Apr. 4/2: ‘Absent-Minded Beggar’. Having got too much liquor, Samuel Lavery, a discharged soldier, wandered into another compartment [...] and appropriated the articles.
1915		Portsmouth Eve. News 19 June 6/2: Arthur Barke,r a soldier, stationed at Hursley Camp, may be counted among Rudyard Kipling’s Absent-Minded Beggars.