The Fire Is In.

I just watched Orson Welles’ 1952 short ghost movie Return to Glennascaul (silly but gorgeous) and was struck by the phrase “keep in” used of a fire: the narrator meets a couple of women at a crossroads, drives them to their isolated house, and is invited in for “tea, or perhaps something stronger,” and the older of the women is pleased to find that “the fire has kept in.” I’d never heard or seen that expression (that I remember), so I went to the OED, and sure enough, s.v. keep (entry from 1901):

to keep in
[…]

3. To keep (a fire) burning: cf. in adv. II.ii.14. Also intransitive of a fire: To continue to burn.

1659 As culinary fire must be kindled and kept in by external materials.
J. Arrowsmith, Armilla Catechetica 160

1711 They observe the law..which orders the Fire to be always kept in.
J. Addison, Spectator No. 72. ¶7
[…]

1849 The fire..keeps in well twelve hours.
Journal of Royal Agricultural Society vol. 10 i. 149

1892 The fire can be kept in all night.
Review of Reviews 15 March 299/1

And s.v. in (entry revised 2021):

I.ii.14. Of fire or light: burning, lighted. Chiefly in to keep in 3 at keep v. […]

1610 Euen in the beginning there went from Enoch a pregnant prophecie of it ending, yea and before the first floud was out, the last fire was in.
W. Leigh, Dreadfull Day i. 14
[…]

1711 They observe the law..which orders the Fire to be always kept in.
J. Addison, Spectator No. 72. ¶7
[…]

1883 By 3 o’clock the electric lights were in, as though it were in the evening.
Liverpool Daily Post 28 December 5/3
[…]

1893 We..sat round the..fire, which we kept in more for the sake of cheerfulness than warmth.
Argosy January 23

1939 ‘Isn’t there a fire?’ ‘Well, it might’ve kept in.’
G. Greene, Confidential Agent iii. i. 224
[…]

2016 What’s the best way to keep your fire in overnight for a warm boat when morning comes?
T. Jones, Narrowboat Guide 167/2

I continue to deprecate their not bothering to name authors; for example, the 1893 Argosy citation is from “The Strange Story of Our Villa,” by M[ary] E. Penn (perhaps a pseudonym of Ellen Wood). In any case, since there’s a 2016 citation, I presume the locution is still in use; are you familiar with it?

Also, as is said (portentously) in the movie, Glennascaul means ‘glen of the shadows,’ and scáil is the word for ‘shadow’ given in my pocket Irish/English dictionary (eDIL s.v. scáile)… but there’s no Wiktionary entry!