Jujitsu is spelled in many ways. But it generally means the flexible art. It was what the Bushi (Samurai) used as self defense when he would loose his weapon during combat. Most techniques would be used against an armed attacker that was wearing armor. Hence the wrist locks to disarm or control the opponents weapon.
The history of Jujitsu is a long one, so no need for detail. But in general that Jujitsu means.