From Paterva Wiki
A person in Maltego has a firstname and a surname. Previous versions supported middle names, but in the end it was determined that this just confusing for users (firstname was seperated from lastname with a comma ','). In this version the name will be everything before the first space. Entering a name such a Jacobus Hendrik van Wyk will thus identify the firstname as 'Jacobus' and the last name as 'Hendrik van Wyk'. While this may appear to be a problem it does not make a huge difference in the performance of most transforms.
Properties of this entity in Maltego
The additional fields used in the Person entity is very important. It can make the difference between getting a lot of false positives and finding the right person.
(Additional search terms) This field is used to focus the search. When looking for a person called "John Smith" and not populating this field Maltego will certainly provide you with useless information. But - if you know that John Smith is a software engineer you should add an additional search term of 'software engineer' - this will add the term to every search and you will have a better chance of finding the person you are looking for.
(Country (Short Code)) This field limits the query to results in a specific country (or TLD). The ISO 3166 country codes can be found at wikipedia. When used in conjunction with the additional search term you can ensure that you will be looking in the right place.