Peppercorn rent is a term given to a nominal amount paid to rent a property. This means the landlord does not receive a payment each year in cash. The terms of a lease state that some form of rental payment must be made. However, there are situations whereby the owner of the land or property concerned does not wish to charge a person any notable amount in rent. Since something must be paid, a nominal sum is chosen to fulfil the terms of the lease.
The name originally came from landlords who charged tenants one peppercorn (yes, a real one) for the rental price of the property. Today, most peppercorn rents will stipulate a sum of money, i.e. £1, to ensure the terms of the lease are met. However, token rents can also be requested, such as the original peppercorn that led to the name.
The payment may not be worth much, but it serves the role of establishing the existence of the lease. This means both parties will be subject to the terms of the lease. The payment covers the ground rent for the property, which today may be worth any amount of money. The rent covers the upkeep of the property while being rented to the tenant. If the landlord decides that only a nominal payment is required, this would be termed a peppercorn rent. It does not need to be £1, but it should be small enough to warrant the term being used. If £50 was charged, it would likely not be referred to as such.