What are the indigenous English words for a prostitute?

The only three Old English words I know referring to prostitutes are meretrix (a direct borrowing from Latin), for-legis (and similar forms, though they tend to also mean adulterer and rarely survived Old English), and miltestre (possibly based on meretrix, which makes it into the Middle English Dictionary as prostitute). All tend to appear in religious writing.

After that, the Oxford English Dictionary has whore (from about 1100, spelled without the [w] (ex. hore, hour) until the 14th century), and the Middle English Dictionary has gigelot and nyhtwerm. Again, these tend to appear in either Biblical or negative contexts in the sources I know of. For example, here's one example of gigelot:

Furmest in boure

were boses ybroht;

Levedis to honoure

ichot he were wroht;

Vch gigelot wol loure

bote he hem habbe soht,

Such schrewe fol soure

ant duere hit hath aboht

In helle ... (lines 23-31)

[First into the chamber were brought hair buns over cheeks; to honor ladies I know they were made; every courtesan will scowl unless she has obtained them. This shrew very bitterly and dearly has bought it in hell.]

So even in this example, gigelot is being used to chastise women for pride in their dress.

This is a topic for specialists, of whom I am not one. You have obviously done a lot of research yourself.

Forgive the liberty but I have to correct your title and a premiss it contains. You will look for "indigenous English" words in vain and indeed for an indigenous English people. I am sure you know that the Celts probably came across from what is now continental Europe, that later the Romans invaded, bringing with them soldiers and hangers on from all over the Roman empire, after which the Saxons and Vikings, one after another, came and brought with them various teutonic dialects and languages, which gradually evolved into something we call English. Britain has been an island of invaders and immigrants right back into the mists of prehistory.

I suspect that sex working is as old as cities are and no older. I also suspect that for that reason it has cousin professions that are just as old, those made necessary by the existence of cities.

However, I find an article on the history of prostitution in Wkipaedia, which is worth looking at. https://en.wikipedia.org/wiki/Prostitution_in_the_United_Kingdom#Medieval_period

It points out, of course, the finds of Roman tokens by the Thames, which may have been admission tokens to brothels. The Romans had their own words for sex-worker: they range in descending order of disrespect: meretrix is a courtesan, understood to have some sort of relationship with the client; lupa means she-wolf; scortum means skin and is a neuter noun.

But then it goes on to the Mediaeval period and the brothels clustered in Southwark in London. And the regulators seem to have been the Bishops. It go on to narrate

1161 a parliament of Henry II introduced regulations allowing the Bishops to license brothels and prostitutes in the area, which became known as the Liberty of the Clink. As a result, brothels multiplied in the Bankside part of the Liberty. They were popularly known as "stew-houses" as many were also steam-filled bath houses.[31] The bishop was their landlord,...

They seem to have been strictly regulated.

Records of court proceedings indicate that priests, monks and friars were among their clients.[32] The brothels had to allow weekly searches by constables or bailiffs, and could not charge prostitutes more than 14 pence per week for a room. Opening was not permitted on holidays, and forced prostitution was prohibited. Prostitutes were not allowed to live at the brothels or to be married, and they were required to spend a full night with their clients.

From this account, I get a variety of words. But most striking is that of Winchester Geese. This is because they seem to have come under the jurisdiction of bishops of Winchester Palace (the bishops of Winchester), who, by the way, profited from this trade.

According to my American Heritage College Dictionary (usually correct on etymology), whore descends to modern English from an Indo-European root, west Germanic, Old English, and Middle English. Is that sufficiently 'indigenous'? Perhaps more gently the same Indo-European rood is credited with giving us caress.