A one name study is a project researching all occurrences of a surname across the world, as opposed to following just the ancestors or descendants of one person or couple.
The surnames Pennyfather, Penneyfather, Pennefather, Pennyfeather and Pennifather are registered with the 'Guild Of One Name Studies' which is the world's leading organisation for one-name studies.
The Guild is a charitable organisation dedicated to promoting the public understanding of one-name studies and the preservation and accessibility of the resultant information. Founded in 1979, the Guild now has over 2000 members spread across the world, studying over 7500 individual surnames.
http://www.one-name.org/