Language questions

Why is it that some use 'log in/log out' and others use 'log on/log off'? Prepositions are always causing problems, aren't they?

According to Lacan, mental illnesses in order of seriousness are: neurosis, psychosis and perversion. So from the second we have 'a psycho', and from the third we have 'a perv'. But what about the first?

The verb 'iterate' means 'to repeat something'. But then we also have the verb 'reiterate' , which is a case of 're-repetition'. Interesting. Someone should do a corpus-based study of the use of these two verbs and detect stylistic effects, right?

Mai