photograph: Job Centre Guide

Of Germanic origin, the noun dole is from Old English dāl, meaning division, portion, share (dāl was a parallel form to dǽl, which is the origin of the noun deal).

From Middle English onwards, dole has been used in the sense of food or money given in charity. For instance, The Brut or The chronicles of England, composed around 1400 (edited by Friedrich W. D. Brie – London, 1906), tells that, because Henry V’s father, Henry IV, “had deposed by his labour þe gode King Richard, & pitousely made him to dye”, the Pope decided that Henry V

sholde, euery weke, on þe day as it cometh About of his deth [= Richard II’s death], have […] A dole to poure peple¹ al-wey on þat day, of xjˢ viijᵈ, to be delyd² penny mele³.

¹ poure peple: poor people
² delyd: dealt, i.e. shared
³ pennymeal: at the rate of a penny to each

Since the end of the First World War, dole, usually preceded by the definite article the, has been the British-English popular name for the various kinds of weekly payments made from national and local funds to the unemployed. The earliest instance that I have found is from The Yorkshire Post (Leeds, Yorkshire) of 24^th April 1919:

EDUCATION AUTHORITIES AND OUT-OF-WORK DOLE.

In consequence of the decision of the Ministry of Labour to extend the operation of the out-of-work donation scheme to November 24, 1919, the President of the Board of Education has decided to extend to the same dale, the period during which the Board will refund expenditure, incurred by local education authorities in connection with the provision of unemployment centres for juveniles, established and approved in accordance with the scheme published by the Board.

On 30^th April of that year, the same newspaper reported the following:

COMMONS DEBATE FOR OUT OF WORK DOLE

[…]
Parliament reassembled yesterday. In the House of Commons, on a vote for £1,935,000 for the Ministry of Labour, Sir Robert Horne⁴ defended his Department, and Government policy with regard to the out-of-work pay. The total estimates for the Department, he said, are £28,000,000, of which £25,000,000 is for unemployment benefit. The decision of the Government to reduce, after May 24 next, the rate of the donation, except for ex-soldiers and sailors, he expects to remove temptations to idleness. But, of a million people drawing the donation, 350,000 are ex-members of the Forces. The Minister expressed the opinion that the abuse of the dole has been exaggerated, but forecast rigorous measures to prevent exploitation of the State’s generosity, and announced that a committee is to be appointed to inquire into the administration of the benefit. Since February, not more than 50 per cent. of those who received the original benefit have applied for its continuation. There is no need, he thinks, to take a despairing view of the situation.

⁴ the Scottish businessman, advocate and Unionist politician Robert Horne (1871-1940)

Therefore, to be, or to go, on the dole means to be, or to start being, in receipt of unemployment benefit. The earliest instance of on the dole that I have found is in the following title from The Observer (London) of 6^th January 1924:

GERMAN UNEMPLOYMENT FIGURES.
3,500,000 ON THE DOLE.