Green’s Dictionary of Slang

(US) spirit, morale.

1913		Eve. Times (Grand Forks, ND) 6 Jan. 4/4: In the majority of cases two or three returns from the big show serve to get a recruit’s angora and his ‘dauber’ goes down.
1925		R. Lardner ‘Women’ in Coll. Short Stories (1941) 154: The boys were depressed. In their own language, their dauber was down.
1947		C. Willingham End as a Man (1952) 158: Don’t get your dauber up, let me explain.
1952		W.R. Burnett Vanity Row 80: ‘He plays a nice piano,’ said Wesson. ‘Soothes me no end when my dobber’s down’.
1967		(con. 1920s) J. Thompson South of Heaven (1994) 117: He [...] told me to keep my dauber up.