The following definition of the slang adjective hot-arsed is from Slang and its Analogues Past and Present. A Dictionary, Historical and Comparative, of the Heterodox Speech of all Classes of Society for more than Three Hundred Years ([London]: Printed for subscribers only, 1893), by the British lexicographer John Stephen Farmer (1854-1916) and the British author William Ernest Henley (1849-1903):

Hot-arsed, adj. phr. (venery).—Excessively lewd. [Of women only.]

The adjective hot-arsed occurs, for example, in A Portrait of the Artist as Australian: L’Oeuvre bizarre de Barry Humphries (Montreal: McGill-Queen’s University Press, 2004), a critical assessment of Barry Humphries’s career ¹, by Paul Matthew St Pierre:

No poet says it—the word “arses”—more eloquently than Humphries, with the possible exception of Marcel Duchamp, whose painting of a mustachioed Mona Lisa bears the inscription L.H.O.O.Q. ², which is homonymous for “‘elle a chaud au cul’ or ‘she has a hot ass,’” and, alternatively, “she is hot-arsed” (St Pierre’s translation).

¹ Barry Humphries (born 1934) is an Australian comedian.
² L H O O Q, by the French artist Marcel Duchamp (1887-1968), was published as follows in 391 (Paris, France) of March 1920:

TABLEAU DADA par Marcel DUCHAMP

L H O O Q

The earliest recorded use of the adjective hot-arsed is from The Confession of the New Married Couple, Being The Second Part of the Ten Pleasures of Marriage. Relating The further delights and contentments that ly mask’d under the bands of Wedlock. Written by A. Marsh. Typogr. (London: [s.n.], 1683):

I know wel enough there will come some times a whiffling blade, that will be relating one or other long-nosed story, hon [= how] like a drunken Nabal, he was well instructed by his prudent and diligent wife; and how little that he would obey or listen to the commands of so brave a Captain; but they will very seldom or never say any thing what grounds or provocatives they have given her for so doing.
Nevertheless my intent is, not so much to flatter the evil or bad natured women, as if their throwing out their ire upon their husbands, had alwaies a Lawfull excuse or cause. Just as Xantippe did, who was Socrates’s wife, think that she had reason enough on her side to scold, brawl at, and abuse that wise and good natured Philosopher, and to dash him in the face with a whole stream of her hot Marish piss. Or that it did any waies become that hotar’sd whorish Faustina, to govern that sage and understanding Emperor Marcus Aurelius.

The adjective hot-arsed occurs on several occasions in My Secret Life (Amsterdam: Privately printed for subscribers, 1888), the account, by a Victorian gentleman, of his sexual experiences:
—the following extracts are from My Secret Life as reprinted in 1966 by Grove Press, Inc., New York City:

I fucked her whenever she went out. She was getting hot-arsed, and she liked the poking.
[…]
I wanted a change, and began to look out for a nice fresh servant. I have now had many servants in my time, and know no better companions in amorous amusements. They have rarely lost all modesty, a new lover is a treat and a fresh experience to them, even when they have had several, and few have had that. They only get the chance of copulating once a week or so, they are clean, well-fed, full-blooded, and when they come out to meet their friend, or give way with a chance man on the sly, are ready, yielding, hot-arsed, lewd, and lubricious. Their cunts throb at the first touch of a finger, and moisten, and they spend freely and copiously. No women’s cunts are wetter, than a young healthy servant’s is after the first fuck on her night out. No one will take more spunk out of a man, and give more herself than the lass who says, “I couldn’t get out before,—I’m sorry you had to wait,—I must really get back by ten.” How they kiss in silence,—how they feel the first lunge of the prick up them,—what pleasure they quietly show,—how they love you, and die as your hot spunk spurts, and their cunt liquidizes.
[…]
Randiness in a woman shows itself in some respects in the same way [as randiness in a man], but it gives much less outward sign.—[…] If she is of a very sensitive, or warm nature, or what is called “hot arsed” or hot cunted, or “randy arsed”—and this lewedness has continued for a long time without the relief given by fucking, she is subject to hysterics.
[…]
How strange is lust or love. In all countries the harlot is the same. All nationalities use the same incitements. In all parts of the world I have found it so. Black or white, in hot or cold countries, all play with male, and the male with the female in the same manner; and I believe, if we could get at the fact, that married, and what are called chaste women, do the same with their husbands. That all men, with all women, in fact, do the same, for they all have pricks or cunts, and prick and cunt are mutually provocative of each other to sensual play, before they kill their lust for the time, in each other’s arms by fucking. Variety and range depend on the sense of beauty, which one or both of them possesses, and on their natural salacity, for there are certainly cold-arsed, if there are hot-arsed women—and equally so—men, who seldom want a woman, nor think of them till they do; whilst others are thinking of women always, during every unoccupied moment of thought.