From the Super Mario Wiki
Jabits (along with Ninjas) are the security of Smithy Gang and are usually wandering around Smithy's Factory. Jabits are apparently easy to make in large numbers because their usual plan of attack is self-destructing. They are often accompanied in battle by Mad Mallets and Poundettes. Also, in the assembly line section of the factory, Mario can observe the process of Jabits being manufactured.
There is an unused enemy in Super Mario RPG named "Drill Bit". Drill Bits are recolors of Jabits and are presumably stronger or weaker versions of them.
Jabit's name comes from a portmanteau of "jab", meaning "to poke or thrust a sharp object", and "bit", as in "drill bit" (which is what they are).
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