Difficult is etymologically related to Difficulty. 
Shake is related to Nod. Nod is related to Approval. Pride is a type of Approval. Pride is related to Gay. 
Difficult --EtymologicallyRelatedTo--> Difficulty 
Shake <--RelatedTo--> Nod <--RelatedTo--> Approval <--IsA-- Pride <--RelatedTo--> Gay 