Have a Screw Loose

Etymology:

• In 19th century, during the beginning of machine era, different tools such as screws, nuts and bolts were used to fix or hold machines tightly. If a screw comes untied and slacks off, the machine would not operate properly and might work in an unusual way. We know since screws are not used for people to hold them tightly, but if a person acts in strange and odd way, this expression can be used to fit him well describing his absurd manners.