From Wiki
the term was further refined into mental and moral imbecility.[1][2] The concepts of "moral insanity," "moral idiocy," and "moral imbecility," led to the emerging field of eugenic criminology, which held that crime can be reduced by preventing "feeble-minded" people from reproducing.[3]

I found this listed in the pension records of a soldier. I was shocked at first and then realized it had another meaning which means he could have had Alzheimer's