Visuddhimagga XVI
- As to derivation, 3. division by character, et cetera: here, however, firstly “as to derivation” [of the word dukkha (suffering):] the word du (“bad”) is met with in the sense of vile (kucchita); for they call a vile child a du-putta (“bad child”). The word kham (“-ness”), however is met with in the sense of empty (tuccha), for they call empty space “kham.” And the first truth is vile because it is the haunt of many dangers, and it is empty because it is devoid of the lastingness, beauty, pleasure, and self conceived by rash people. So it is called dukkham (“badness” = suffering, pain), because of vileness and emptiness.