The term originated by the more experienced hackers to refer to the novice hacker who rely on readily available scripts and programs, created by the experienced hacker, instead of using programs that they had made on their own. This generally leads to this type of hacker being caught more often than an experienced one. Though they are not as dangerous as the experienced hackers, they are still considered dangerous. They tend to run programs that scan the entire Internet for vulnerabilities and then mass hack them as soon as they are found.
Source: https://www.bleepingcomputer.com/glossary/script-kiddy/