Expression of disgust at endlessly bad breath (3)

I believe the answer is:
bah
'expression of disgust' is the definition.
(as in 'bah humbug!')
'at endlessly bad breath' is the wordplay.
'at' means one lot of letters go next to another.
'endlessly' means to remove the last letter.
'breath' becomes 'h' (I can't justify this - if you can you should give a lot more credence to this answer).
'bad' with its last letter taken away is 'ba'.
'ba' next to 'h' is 'BAH'.
Can you help me to learn more?
(Other definitions for bah that I've seen before include "Exclamation of contempt or disgust - Scrooge used to say it" , "Exclamation of disgust or annoyance" , "''... Humbug'' Scrooge's cry" , "Expression of disgust or contempt" , "''...! Humbug!'' (Scrooge)" .)
