Green’s Dictionary of Slang

humdrum n.

[SE humdrum, a dull, monotonous person; ult. SE hum, to murmur on]

1. a wife, a husband.

[UK]Partridge DSUE (8th edn) 581/2: C.17–early C.19.

2. a parson.

[[UK]T. Randolph Hey for Honesty II i: stiff: Vaith, would Master Clip-Latin our vicar were here too [...] lack: Aye, and I like him. He’s none of the humdrums, he’ll clap it up quickly].
[UK]N. Ward Compleat and Humorous Account of Remarkable Clubs (1756) 251: Here sat a High-Church Parson, a man of Wit and Learning, between a couple of fanatical Hum-drums.