Apart from sicken and sickness, other derivatives are from Germanic languages, such as siech, ziek, syg, syk, and sjuk in German, Dutch, Danish, Norwegian, and Swedish, respectively.
Sick means ‘affected by physical or mental illness, not healthy’, a word that can be applied to the collective, such as “The British economy remains sick.”
Erich Fromm, a social psychologist, much influenced by Karl Marx and Sigmund Freud, used this collective sense of sick as an attribute of ‘Western civilization’, confirming what I had intuitively seen during my formal education from the late 1940s to the early 1960s, from my innate sense of Wholeness.