ケン 
けわ.しい 
() impassable terrain () dangerous
              
けわしい (adj-i) (1) precipitous, rugged, inaccessible, impregnable, steep, (2) grim, severe, stern
けんあく (adj-na,n) dangerous, serious, gloomy, perilous, threatening, stormy

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Etymologies: 中文字譜 : 説文解字