The kanji 疾疾 primarily conveys the meanings of "rapid," "quick," "swift," or "sudden," often in the context of speed, or the onset of something, such as an illness. It can also imply something painful or unpleasant that occurs quickly.

・On-yomi (音読み): シツ (shitsu) ・Kun-yomi (訓読み): やまい (yamai)

⚫︎疾走 Translation: Sprint; dash; race ⚫︎疾風 Translation: Gale; swift wind ⚫︎疾病 Translation: Disease; illness

The kanji 疾疾 is a phono-semantic compound (形声文字). It is composed of the radical 疒 (やまいだれ - yamai-dare), which means "sickness" or "illness," and 矢 (や - ya), which means "arrow." The 疒 radical indicates a connection to illness or physical condition. The 矢 component provides the phonetic element (shitsu) and also suggests the speed or suddenness of the illness, like an arrow rapidly hitting its target. The combination thus evokes the idea of a sudden or swift onset of illness.