What are some of the different words ralph and jack use to describe how crazy the littluns are to be afraid of the beastie?

Referring to lord of the flies

They used words like "crackers" or "batty".

The words above are very common to be used in British vernacular as slangs that often come out in the conversation between common people.

Those are the type of language that commonly heard by the author William Golding in his young age.