ک ب ک بk-b-k-b
quadriliteral كَبْكَبَ يُكَبْكِبُ كَبْكَبَةًkabkaba yukabkibu kabkabatan: to throw down headlong again and again, to hurl tumbling. The lexicographers say it is a reduplication of k-b-b, and the reduplication produces intensity — that is, not once but throwing down headlong time after time. Only once in the Quran: ﴿فَكُبْكِبُوْا فِيْهَا هُمْ وَالْغَاوُۥنَ﴾ (Ash-Shuʿarāʾ 26:94).