Buddy is a synonym of Mate. Mate is a synonym of Couple. Couple is a synonym of Handful. Handful is derived from Hand. 
Employ is related to Worker. Observer is a type of Worker. Observer is a type of Expert. Investigator is a type of Expert. 
Buddy <--Synonym--> Mate <--Synonym--> Couple <--Synonym--> Handful --DerivedFrom--> Hand 
Employ <--RelatedTo--> Worker <--IsA-- Observer --IsA--> Expert <--IsA-- Investigator 