Green’s [invaluable] Dictionary of Slangdates the first documented use of the word ‘fag’ to mean a cigarette as 1888, in the Saturday Review
They…burn their throats with the abominable ‘fag’, with its acrid paper and vile tobacco
‘To fag’, according to GDOS, means first ‘to beat’, then ‘to make someone work hard’ or ‘to work hard’ (presumably including the context of the Eton College model of younger boys acting as servants to older boys), and then ‘to move quickly or with an effort’, and then ‘to supply with a cigarette, or to smoke’.
An article in the Arbroath Herald, 4 October 1918, reads as follows:
After the band had bestowed its benediction in the strains of “Return to Serbia,” the writer was fortunate enough to “fag” an interpreter, through whom he sought out the native Scoutmaster.
This seems to show ‘fag’ being used as a verb, meaning ‘get hold of’ or ‘secure the services of’, which seems to be linked to the ‘school servant’ idea. This use of ‘fagging’ in wartime, beyond the school bounds, can be found in Interned in Germanyby Henry C Mahoney (1918), but the ‘fagging’ involves being paid in ‘fags’, slightly confusing:
Another occupation was created by the residents in the lofts and horse boxes, who appointed orderlies to keep the barracks clean and neat. The appointment lasted as long as the orderly cared to hold it. His weekly salary was paid by the occupants, the usual contribution from each being 10 pfennigs—one penny—per week, although some of the wealthy prisoners gave more. In the horse boxes, this service was supplemented by that of “fags.” The fag was not posted to a single box but had a regular round of patrons. His duties were keeping the apartment clean, making the beds and performing similar services. The average weekly payment for this was about S shillings a box. When a prisoner was fagging to three, four or half a dozen boxes regularly, his weekly aggregate was not to be despised.
In The Grey Brigade ( a trench – actually camp – magazine of a group of London-based territorial regiments) on 26 June 1915 we find:
What is to be done with the inveterate cigarette obtainer – the man who always has a box of 50 in his kit-bag but none in his case? He is to be found in all companies. “Got a fag, old man?” is the favourite opening. The only way of escape, it seems to me, is to form an S.F.C.O.U.F. – Society For Choking Off Undesirable Faggers.
Any more interesting wartime fags would be most welcome.