The colloquial phrase no names, no pack drill is used to indicate that the person or persons guilty of a misdemeanour will not be named, in order to spare them recrimination.

The noun pack drill denotes a military punishment involving a lengthy period of marching up and down carrying full equipment.

These are the earliest occurrences of the phrase no names, no pack drill that I have found, in chronological order:

1-: From the column Multum in parvo ¹, published in The Westmeath Guardian. And Longford News-Letter (Mullingar, Westmeath, Ireland) of Friday 16^th May 1890:

Who was the gentleman with the tall hat in the Police Court on Saturday? It was real silk and glistened in the morning sun. Some were kind enough to say it was that very voluble gentleman, Mr Peter ——. However, no names no pack drill; and I may say he looked well with the tile on.

¹ The Latin phrase multum in parvo, literally much in little, denotes much information condensed into few words or into a small compass.

2-: A soldier with eighteen years’ service signed with No Name, no Pack Drill a letter explaining the causes of suicide in the army, published in The Evening News and Post (London, England) of Thursday 31^st July 1890.

3-: From an article about military manoeuvres, published in the Weekly Dispatch (London, England) of Sunday 12^th October 1890:

Of all the communications, that from a gunner of the 1^st Kent Artillery is the most amusing. “No name, no pack drill” is an axiom in the army, and, having had much to do with Regulars as well as auxiliaries, I will not divulge the name of the gunner.

4-: From the Rochester and Chatham Journal and Mid-Kent Advertiser (Rochester, Kent, England) of Saturday 21^st March 1891:

The last of the public meetings in support of the Conservative candidates for election to the Chatham Town Council was held on Tuesday evening […].
[…]
Mr. Breeze said a man of large property said to him “Keep a school board away.” […] The gentleman who said “Keep a school board away” would not give a penny-piece for rebuilding the British Schools. He had a lot of property, but when he was appealed to he said “I want a School Board. I have altered my opinion.” That was a gentleman who was now putting up for that ward (cries of “Name” and a voice “No names, no pack drill.”) No names no pack drill was right. The gentleman’s conscience would prick him when he read what was said (a voice “It’s Philpott” laughter).

5-: From The Civil and Military Gazette (Lahore, Punjab, Pakistan) of Thursday 27^th August 1891:

A Growl from Sergeant Atkins.

[…]
Sir,—The “Growl” you published on 21^st inst. from “Bed” has already taken good effect, as the Sergeants Mess complained of is at last to be furnished in a decent manner. Therefore I trust you will insert this “growl” from Tommy Atkins, and it is to be hoped that the same good result will follow.
First I will take the Temperance Room. On the arrival of my regiment (no names, no pack drill) at Pindi last winter a branch of the Army Temperance Association was formed, and a number of N. C. O’s and men joined it, but soon after the regiment took over the town barracks the Secretary fell sick, and on stock being taken by an independent party a large deficit was discovered. There was no enquiry made into the matter to see who was to blame, but the Temperance Room was closed, and for the past two months this regiment has had no Temperance Room open. Consequently the majority of N. C. O’s and men who did belong to the A. T. A. are drinking, as they got no encouragement to keep on the “tack,” and had no place in which to pass their spare time. The Blue Book issued on Regimental Institutions states that a Temperance Room will always be kept open in every regiment, and if it does not pay a grant will be made from time to time by the C. O. from other funds to keep it going, so that somebody is to blame for the permanent closing of our Temperance Room.

6-: From The Western Times (Exeter, Devon, England) of Monday 28^th May 1894:

A friend of mine sends me the following account of the training of the Yeomanry. He tells me that the allusions to putting in the “mangold,” “picquet duty,” and the “effigy” will be thoroughly understood by all who took part in the training, although no names are mentioned, for as he truly says—“No names no pack drill.”

7-: From The Wigan Observer, and District Advertiser (Wigan, Lancashire, England) of Friday 22^nd February 1895:

The following is an extract from a letter, received a few weeks ago, from a young Wiganer who is a member of that gallant little force which fought so bravely in the late Matebele war ², viz., the Bechuanaland ³ Border Police:—
[…] There is rather a good thing to be made out of transport riding, that is, running goods from Mafeking to Bulwayo at a very stiff tariff. I know one member of a noble house who is making a tidy living out of it, but “no names—no pack drill,” as we say in the service.

² The First Matabele War (October 1893 – January 1894) was fought in modern-day Zimbabwe between the British South Africa Company and the Ndebele (Matabele) Kingdom.
³ Bechuanaland is the former name of Botswana, a landlocked country in southern Africa.

8-: From the account of a bare-knuckle boxing match that had taken place in South Africa, published in The Sporting Life (London, England) of Wednesday 20^th March 1895:

Some time was now lost by the appointment of a referee. Many were proposed and agreed by both sides, but it seemed as if none could be enticed to act. In vain were the eligible reminded that they had little or nothing to fear from the minions of the law, as the men who were about to battle had not a cent. on the issue. Just when it seemed as if the non-acceptance of the onerous post was going to prove an immovable obstacle to the commencement of hostilities, a member of the fancy—well-known for his straightness (but who shall be nameless—for no names no pack drill, and brother scribes please note) volunteered to fill the unthankful office.