The colloquial British-English noun munitionette designates a female worker in a munitions factory, especially during the First World War (1914-18).

This noun occurs, for example, in In the line of fire, by Gerard De Groot, published in The Scotsman (Edinburgh, Midlothian, Scotland) of Thursday 2^nd March 1995 [No. 47,256, page 19, column 2]:

Total war caused shortages of labour which brought opportunities for women.
By working in munitions factories during the First World War, women participated in the killing process. But making shells was sufficiently far removed from actual killing for this work to be deemed acceptable. The prevalent imagery used to depict these workers nevertheless suggests a certain unease within society.
Photographs of women in munitions factories were rarely published in Britain because images of sweating, dirty women working at brutish masculine machines apparently damaged morale. Instead, a popular painting showed a “munitionette” in feminine dress, with sweet curls flowing from a neat bonnet, cuddling a shell as if it was a baby.

The noun munitionette is from:
– the noun munition,
– the suffix ‑ette, forming nouns denoting women or girls linked with, or carrying out a role indicated by, the first element, as in suffragette and usherette.

The earliest occurrences of the noun munitionette that I have found are as follow, in chronological order:

1-: From Trade Union Gossip, published in The London Illustrated Weekly (London, England) of Thursday 4^th November 1915 [Vol. 3, No. 64, page 225, column 2]—the Welsh politician David Lloyd George (1863-1945) was the Minister of Munitions from May 1915 to July 1916:

MUNITIONETTES. Women munition workers have been granted by the Minister of Munitions a weekly wage of £1 per week, or, when doing fully skilled work, the time rates of men doing similar work. Overtime to be paid for exactly as in the case of men, and 15s. per week if unable to work through breakdown, air raid, or other such causes.

2-: From The Lincoln Leader. And County Advertiser (Lincoln, Lincolnshire, England) of Saturday 20^th November 1915 [No. 974, page 8, column 6]—the following is about Private W. G. Oncken, who was training with the Machine Gun Section of the 2/23^rd London Regiment (T.F.):

Here is a sample of Pte Oncken’s happy style of narrating his impressions. He is referring to munition workshops in the town where he is billeted. “One of these is just by our Battalion parade ground., and it is a hard matter to judge whether the boys in khaki, rifle on shoulder, or the girls in holland and blue, who smile over a shell hand, make a braver show. Quite a lot of the nice girls of the district, in fact are munitionettes.”

3-: From Trade Union Gossip, published in The London Illustrated Weekly (London, England) of Thursday 9^th December 1915 [Vol. 3, No. 69, page 325, column 2]:

A PIE-CRUST PROMISE. It appears that the promise made by Mr. Lloyd George of a minimum 20s. wage to women munition workers applies only to factories actually run by the State, such as Woolwich Arsenal, and not to the thousand factories controlled by the Government. It is true that the masters of the controlled factories are piously recommended to pay the pound, but it is equally true that they impiously fail to do so, and there is widespread disaffection amongst munitionettes in consequence.

4-: From The Macon News (Macon, Georgia, USA) of Thursday 16^th December 1915 [page 7, column 4]—Sylvia Pankhurst (1882-1960) was a British feminist, socialist activist and author:
—Note: unfortunately, this article contains many typographical errors:

GIRL-LABOR CRY IS HEARD IN LONDON
MUNITIONETTES WITH $1.50 A WEEK PLEA FOR EQUAL WAGE IN LONDON FACTORIES, MRS. PANKHURST WRITES.
By SYLVIA PANKHURST.
(As Told in Interview by Mary Boyle O’Reilly.)

(Miss Pankhurst, the daughter of the famous British suffragette, has given up feminine frightfulness for adventures into adversity and has become a recognized leader among the groping workers of East London.)
Bread is 16 cents a loaf in London and the price is rising. Three million wage earners are under arms—probably—a million wives to feed alone in war time.
Comment on these facts to the fair weather philanthropist and the answer is an invariably: “But consider what women now earn in munitions factories.”
“Well, let us “consider” the wage scale of munitioinettes.
Making munitions is admittedly a dangerous work. Women entering many of the shops must change their boots for special slippers, assume overalls and discard their hairpins and wear fireproof caps. A nail, a bit of wire might cause an explosion. People should be paid for taking such chances.
Sir William Bardmore, the big munition master of Glasgow, declares the work done by women workers in his factories, whether by night or day, is “astounding,” being just as good and just as speedy as that of men. Night work by women is no longer prohibited. While England is under military law (and this threatens to be a long, long war) all labor laws are abrogated. Now the minister of munitions (Mr. Lloyd George) when taking over the munitions of war factories pledged the government to establish an equal wage scale for men and women and to see that there would be no sweated labor.
“We shall not,” said the munitions minister, “utilize the services of women merely to get cheap labor.”
That was months ago. Today British battles are being fought with bullets and shells made by sweated workers.
East London muntionettes who have earned $6,35 a week have been warned that they are making far too much and must accept lower paid processes to bring their wages down. Croydon girls can earn only $2-$3.12 a week, Wolverhamton women from $1.50 to $3 for 55 hours’ work, Walsall munitionettes $3.75 to $4 for a 73½ hour work. And under the munition act wage scales in the thousand and more “controlled factories” can not be altered unless by consent of the munition minister.
Moreover, a munitions maker who attempts to leave one arms factory to seek employment in another can be taken into court by an employer and prosecuted under the munitions act.
Many deputations from trades union and women’s organizations have waited upon the munitions minister to sumbit this scale of weekly wages paid men and women munitions makers doing the same work.
Bedford—Men, $3.75 to $6; women, $2.00.
Herndon—Men, 20c an hour; women 6c an hour.
Sheffield—Men, $5.62 a week; women, $2 to $3 a week.
Those figures point the way to the war that is behind the war. The question of equal pay for men and women is a very serious one for both men and women. If women do men’s work at a lower wage, and prove that they are able and willing to do it equally well, men will either have to accept the lower wage or join the army of the unemployed. And if wages are to be depressed it will prove disastrous for men and women and their children.

The noun munitionette reoccurred during the Second World War (1939-45), as women worked in munitions factories again. The first two occurrences that I have found are from the Cabbages and Kings section of the Sunday Sun (Newcastle-upon-Tyne, Northumberland, England):

1-: Of Sunday 16^th June 1940 [No. 1,090, page 2, column 7]:

A Munitionette, Elswick, declares that whatever slacking there may have been in the Great War, munitions makers are all out to deliver the goods this time.

2-: Of Sunday 25^th August 1940 [No. 1,100, page 2, column 8]:

Hours of War Workers
Last October I started work in a munitions factory. The hours were to be from 7.30 a.m. to 7.30 p.m. on four days, Friday 7.30 a.m. to five p.m.; Saturday, finish at noon. Sunday off duty.
After about three months we had to work every day in the week from 7.30 a.m. to 7.30 p.m., except Sunday, when we finished at five p.m. Our only leisure time was Sunday night which I spent in bed tired out after constant hard work.
Two weeks ago, when everybody was hoping for one or two nights off at five p.m., we were informed that Sunday would be our only day off. . . . I think you will agree with me and all the girls I work with that our hours are far too long.—Munitionette.