The words anal-retentive (or anally retentive, anal retentive), often shortened to "anal", are used in everyday language to describe a person with so much attention to detail that the obsession becomes annoying to other people. The idea was thought up by Sigmund Freud
In the psychology ideas of Freud, the anal stage is said to follow the oral stage of development in babies and young kids. This is usually when they are learning toilet training. Freud made a theory which said that children who experience troubles during this time may develop "anal" personality traits, as well as a general interest in collecting and keeping things.
Although Freud's theories have been influential, research suggests patterns of parental attitudes has a major effect on how a baby will grow up.