キ, こぼ.つ, こわ.す, こぼ.れる, こわ.れる, そし.る, やぶ.る
break, destroy, censure, be chipped, be scratched, be broken, be ruined
JLPT0 G7 S13 F5000
Here, 臼 mortar is an abbreviated form# of a character below which is added 米 rice → grind rice in a mortar. 毀 adds a character combining 土 earth and 殳 action indicator → knead earth/clay (compare 圣 as described in 怪). The combination of elements suggests the idea of destroying by causing to collapse (compare 壊) → *destroy* → *slander* (← words that destroy).
[Full Kanji Etymology List]