Toilet is related to Bath. Bath is the opposite of Shower. 
Rail is etymologically related to Regular. Rail is related to Support. Support is a synonym of Defend. Defend is a different concept from Attack. 
Toilet <--RelatedTo--> Bath <--Antonym--> Shower 
Regular <--EtymologicallyRelatedTo-- Rail <--RelatedTo--> Support <--Synonym--> Defend <--DistinctFrom--> Attack 