Plea is related to Free. Free is related to Bonus. 
Soft is etymologically related to Software. Soft is related to Fur. Fur is related to Cotton. Cotton is related to Bottom. 
Plea <--RelatedTo--> Free <--RelatedTo--> Bonus 
Software <--EtymologicallyRelatedTo-- Soft <--RelatedTo--> Fur <--RelatedTo--> Cotton <--RelatedTo--> Bottom 