Here are some possibilities:
* Nickname: It could be a nickname for a name like "Jiban", "Jyotirmoy", "Jibesh", or any other name starting with "Ji".
* Shortened Form: It might be a shortened form of a longer name, such as "Jiku" for "Jignesh", "Jatin", or "Jyotirmay".
* Foreign Origin: It could be a name of foreign origin that has been adopted into Bengali.
Without more context or information about the person with the name "Jiku", it's difficult to pinpoint the exact meaning.