And this, shortly put, was, in the main, what brought about the state of society known as the feudal system.
It was the more easy for the lesser men, the vassals, and the great man, the lord, to make these terms with each other, because something of the kind was already in existence, both in the Germany from which the Franks came and in the Roman and Gothic society into which they had come as conquerors.
The name given to the assembling of men of less power and wealth around the greater men had been "comitatus," in Germany. In Rome it had been the custom for a prominent citizen to have a troop of "clientes," or clients, men of the people who came to him to ask him for advice about any legal claims that they were making, or any injustice under which they were suffering. They would receive his advice, and perhaps he would speak for them when their case came before the court. In return, these clients would support their patron, as the great man was called, with their votes whenever they could be of use to him, and they would even accompany him about the city, in times of disturbance, as a kind of bodyguard.
The Frankish kings, we may note, had a bodyguard for their special protection, and this bodyguard was held in very high estimation, so much so that if one of them were killed the killer, or his relations, had to pay a penalty three times as heavy as they would have had to pay for the killing of any other free man. So the service of the vassal to his feudal lord was only an extension of the kind of service that the client did for the patron; and so too the service of protection that the lord gave to the vassal might easily grow out of the protection and help given by the patron, to the client.
The "precarium"
And then there was another custom common in the Roman and Gothic society which helped to form the relationship between the vassal and the feudal lord. If a free man were landless he was in a very poor position. It was beneath his dignity to serve as a slave, or even as a "villein," which was a position in society between that of a slave and a free man. But if he were without land, he had no means of livelihood; and as his life was of no value to anyone he had no one to defend him. Therefore it had become usual for these landless free men to come to some large land-owner and offer him to do him certain service if he would grant, or lend, them a piece of land, or possibly the use of a mill—a water-mill for grinding corn—or some other grant out of which they might get a livelihood. If this were granted them, they would give their service and help to the lord. The Latin word for "to pray" is "precari," and so this relationship between the lord and the tenant was called "precarium," because the tenant had "prayed" the lord for it. I have called it a "grant, or loan." It was not a gift, because the lord might take it back at any time, and so end the tenancy, nor could the tenant pass on his right in the land, or whatever it might be, to his heirs. If the lord did allow it to go on to these heirs, they would probably have to pay him some "fine," before they succeeded to it, as well as undertaking to continue the service which the first tenant, when the grant was made, had promised.
So herein, that it could be taken back by the lord, it was like a loan; and yet it differed from a loan in this—that there was no idea in the mind of either the lord or the tenant that it was likely to be taken back. It was intended to be a permanent loan, if we may use that expression, but still it was recognised on both sides that the lord or the lord's successors had the power at any moment of taking it back, if he or they pleased, from the tenant and the tenant's successors. You must have heard the expression "a precarious possession," or something of the kind. You may now know how that expression arose. The word "precarious" is, of course, from this "precarium," which is derived from the Latin word for "to pray."
You will find that these two ideas, that of the relation between the patron and client, and that between the landlord and the "precarious" tenant, helped to form the foundations, the roots, from which the feudal system grew up. The land or the mill was the fee, or fief (fief was the French form of the word) in return for holding which the holder owed service to the lord.
Just what he should do for the lord, by way of service, differed in different places at first, and was determined by the different customs of each place; but as time went on the duties began to be defined, or laid down, more exactly, and grew to be very much the same wherever the system prevailed. The vassal had to follow his lord to war when called on, he had to serve as a defender when the lord was attacked, he was liable to have to contribute to the dowry of the lord's daughter when she was married and to his lord's ransom if he should be taken prisoner by the enemy. He had to follow the lord to battle armed at his own cost, perhaps mounted, perhaps with some of his villeins following him.