From Dragon Quest Wiki

Enfeebler is a skill introduced in Dragon Quest Monsters: Joker.

Dragon Quest Monsters: Joker

Enfeebler is learned by the Goodybag and Skeleton.

Ability Skill Points
Sag 8
Dim 16
Weakening Wallop 28
Stupefying Strike 40
Kasag 55
Kadim 70
Sag Guard 85
Dim Guard 100

Dragon Quest Monsters: Joker 2

Enfeebler is also learned by the Boring bug, and Goodybag X. Its abilities remain unchanged.