Did any English duke ever grant away an earldom he held?

I thought I ought to answer the question rather than simply commenting on another. There are a few points that may help you understand what is going on. I will confine my answer to England because that is where the question is about and this is a subject which varies considerably across different countries.

The basic point - made by a number of users - is that, with very few exceptions, in at least post-Norman England, a title was just that, a title. You could be styled "Duke of X" or "Earl of Y" but those titles were quite separate from the notion of vassalage.

In fact titles on their own conferred very little by way of rights at any time. There were periods when, for example, particular forms of dress were intended to be restricted to particular classes of people, but in general no.

What I think the poser of the question is thinking about in terms of "vassalage" is the notion of someone being someone else's feudal lord.

Now this system operated in England. All land was either "held of" someone else, or was in the hands of the Crown (technically known as "Royal demesne"). So the Manor of Littletown might be held of Lord W who holds of Lord X who holds of Lord Y who holds of the Crown as tenant in chief.

Being Lord of a particular manor or manors was thus a legal relationship concerning primarily land ownership. It was not really a title in the modern sense. Lots of people are "lords", including numerous women, also known as "lords".

These chains of ownership happened because, at first, the holder of land was permitted and even sometimes expected to create subordinate holders by a process of subinfeudation. In the above example, the Crown may have granted lands including the manor of littletown to Y who then granted some of them to X who then granted some of them to W.

But this process began to be used as a way of transferring land to others. If W wanted to sell the manor to another person they would have to get X's permission (as W's lord) or they could simply grant the whole manor to the purchaser. That created a feudal mess. In 1290, Edward I passed the statute Quia Emptores which prevented any further subinfeudation. At that point no new links in the feudal chain could be created (except by the Crown).

The first duke in England (the Duke of Cornwall) was created in 1337 by Edward III by a royal charter that gives it to the eldest son of the monarch (then the Black Prince).

From this it should be obvious that no duke could have created a feudal inferior because the ability to do so was stopped some 47 years before the first duke was created. There may have been situations where an Earl happened to acquire land where their feudal lord was a Duke but that would be an accident. What is more the reverse could have easily occurred as well.

This is because, as I said earlier, just being a Duke or Earl didn't give you any particular local jurisdiction or create a kind of "subkingdom" in which you were a sort of mini-king. You might be made Duke or Earl of somewhere and have no lands there and no authority at all in that area. In the earlier period that would not be usual - why make someone Earl of March if you weren't also going to give them something to do there? But the current Duke of Cambridge has very little to do with the city or county in law.

There are exceptions, but they are really extra rules rather than something inherent in the title.

The big exceptions were the "counties palatine". In those places someone was usually given local power. There were separate judicial and administrative arrangements. I think only one of these was ever held by a Duke (Lancaster) and for most of its history the Duke was also the Monarch as is the case today. But again dukes come too late for the handing out of feudalities.

The Earl of Chester (another county palatine) was much closer to what the questioner had in mind.

The Duke of Cornwall does have certain rights (by charter) such as bona vacantia (the right to receive property that is not otherwise owned, eg if someone dies with no will or near relatives), so its not a nothing title, but these are not feudal rights.

The "Charter of Novadamus" is unknown to English law and so ought not to form part of a correct answer.

They couldn't! All titles were bestowed by the sovereign, you couldn't just say "Oh, I've got a spare earldom etc I don't want, I'll give it to a friend." Apart from any other consideration, your eldest son would be deeply peeved, because he would expect to inherit it!

Also, titles were not attached to land in quite the way the question suggests. When Richard III was Duke of Gloucester, his main landholdings were actually in the North not in Gloucester. The title of Duke was a fairly late import - sorry, can't remember when, but after the Norman Conquest - and originally reserved for the ruling dynasty.