The servant has to DO a strong effort, or face the lash!
make an effort (at improving your French, at quitting smoking, to be nice to your friend's douche boyfriend, etc.) , - Actualy, this is more in common with がんばるthan with the other two つとめるs.（勤めるand 務める）
|努||make an effort||STRENGTH||力|
The WOMAN gets mad, but I dread a CRAFTY man.
Making an effort takes all your STRENGTH.