Fog is related to Mass. Mass is related to Cloud. 
Drift is etymologically related to Drive. Drive is related to Wheel. Wheel is made of Metal. Metal is related to Key. 
Fog <--RelatedTo--> Mass <--RelatedTo--> Cloud 
Drift --EtymologicallyRelatedTo--> Drive <--RelatedTo--> Wheel --MadeOf--> Metal <--RelatedTo--> Key 