Force is related to Plunge. Plunge is a synonym of Fall. Fall is a synonym of Spill. 
Identity is etymologically related to Identical. Identity is related to Citizen. 
Force <--RelatedTo--> Plunge <--Synonym--> Fall <--Synonym--> Spill 
Identical <--EtymologicallyRelatedTo-- Identity <--RelatedTo--> Citizen 