Thin is related to Line. Line is related to Straight. 
Proper is a different concept from Wrong. Wrong is related to Rub. Rabbit is etymologically related to Rub. 
Thin <--RelatedTo--> Line <--RelatedTo--> Straight 
Proper <--DistinctFrom--> Wrong <--RelatedTo--> Rub <--EtymologicallyRelatedTo-- Rabbit 