Odds is etymologically related to Odd. Odd is similar to Unusual. Unusual is the opposite of Ordinary. Ordinary is the opposite of Weird. 
Blow is a synonym of Belt. 
Odds --EtymologicallyRelatedTo--> Odd <--SimilarTo--> Unusual <--Antonym--> Ordinary <--Antonym--> Weird 
Blow <--Synonym--> Belt 