Did they didlum?

When my grandfather Bill was alive, I remember he collected cash from his 3 daughters every week, and gave it back to them before each Christmas. This informal savings club was called a Didlum, as was the money itself, i.e Aunt Mary would ask my mother if she had paid her didlum this week.

I have always been intrigued by this word, and wondered if other families used it. My mother says it goes back a long way: she remembers it from her Luton childhood in the 1940s when it was collected by a neighbour - Mrs Chamberlain. I decided to research the origin and usage of Didlum as part of my List.

I looked in many dictionaries, including the big ones in the library, but it was not there.
I tried emailing a variety of language professors at local universities - not one reply (perhaps if I had enclosed a cheque...)
I asked several family members for information, since I did not know if it was a family word or a local word, or more widely used.

I googled Didlum and found a few references - one was on a discussion board from Nottingham, another was in Cork, and the third was in Birmingham.
The first was a dictionary of Cork Slang by Sean Beecher, and defines didlum as DIDLUM

Construct:	Noun
Definition:	A savings scheme. A group of people contribute an agreed amount over a fixed period of time. The money was not distributed until all of it was collected a the end of the period. Contrast with Manage.
Use:
Derivation:	Unknown

In Nottingham it was used in the same sense, with evidence given of it being used in clothing factories amongst the women.

The Birmingham History Forum has details of a didlum  club, so again, the same meaning.
I struck gold when I found a reference in a history book: They Worked All Their Lives, Women of the urban poor, 1880-1939 by Carl Chinn
 I borrowed the book from Bedford Central Library
On page 71 is this passage:

They Worked All Their Lives: Women of the Urban Poor in England, 1880-1939

 By Carl Chinn

When discussing means of credit, it is important to be aware

that, in spite of their impoverishment, wives of the urban poor

could and did attempt to insure themselves against hard times

through saving. This form of protection was not with a friendly

society or an insurance company; rather it was achieved

through small, highly localised groups of lower-working-class

women. A group of wives would bond together and form a club,

known as a ‘didly club’ in Lambeth and a ‘didlum’ club in

Birmingham. Out of their number, one who was trusted by all

would be chosen to hold the cash and to distribute it at the

appointed time, uually Christmas. Properly known as ‘rotating

credit associations’, the payments increased by the sum paid

in the first week. Thus if a figure of a halfpenny was decided

on - usually the case by the 1920s - then in the first week a

halfpenny was saved, in the next a penny, and so on. If a member

paid up for the full fifty weeks in which the club ran, then a um

of £2 13s lid was saved. For most women it was a struggle to

keep up these payments throughout the full term, but even those

who dropped out before the allotted term still received a not

insignificant sum to help them out.

The colloquial names of these clubs are probably derived from

the belief that those entrusted with clubs’ funds ‘diddled’ or

cheated their members out of their money. This belief arose

because of the disappearance of some trustees with the col-

lection and also because some clubs were in the habit of paying

the collectors with the final week's fee. Yet such clubs were -

and still are - very popular and if swindles had been common

place then they would soon have ceased to exist.

In The Ragged Trousered Philanthropists by Robert Tressell, one of the villains is called Mr Diddlum, as I found out when we read it recently for my Book Club.

So a great success! I found out that it is not just a family name, but used more widely, and it can be spelled with a single or double D.