C20 (originally in the sense: slightly drunk, tipsy): of unknown origin
bonkers for learners of EnglishPowered by COBUILD (bɒŋkəʳz)
adjective [v-link ADJ]
If you say that someone is bonkers, you mean that they are silly or act in a crazy way. [British, informal, disapproval] ⇒ The man must be bonkers to take such a risk. ⇒ I nearly went bonkers with frustration.