The phrase "wast on back of" refers to something located on the backside of the waist. It is important to note that "wast" is an archaic spelling of "waist" and is pronounced /weɪst/. The word "on" is pronounced /ɒn/ and represents a common preposition in English. Finally, the phrase "back of" is pronounced /bæk əv/ and denotes the location behind a particular object or body part. Putting these sounds and spellings together, we get the complete phrase /weɪst ɒn bæk əv/.