A small unit of value or a fractional share, often representing one quarter.
A farthing was a small unit of money, originally equal to one quarter of an old English penny.
In property and inheritance records, a farthing or farthing-deal could also refer to a fractional share or division of rights.
The meaning depends on the context in which the term appears, as historical records used such terms both for money and for shares of property.
See also:
Fine
Inheritance
Reversion