For the 19th, the affliction (part of a nasty cold also featuring paroxysmal coughing) and the name, reproducing bits of Ancient Greek spelling carried through to Latin, French, and then English. From NOAD2:
excessive discharge or buildup of mucus in the nose or throat, associated with inflammation of the mucous membrane. ORIGIN early 16th cent.: from French catarrhe, from late Latin catarrhus, from Greek katarrhous, from katarrhein ‘flow down,’ from kata– ‘down’ + rhein ‘flow.’
(The name catarrh obviously has nothing to do with the Gulf country name Qatar, though the latter is sometimes pronounced the same as the former, /kǝtár/.)
Remedies for catarrh come in two forms: lozenges, pastilles, or (cough) drops narrowly aimed at reducing the coughing symptoms; and herbal remedies with broader aims. A British formulation of the simple cough remedy:
The best-selling American counterpart is Hall’s Mentholypus Drops (more menthol and eucalyptus), which also comes in a honey-lemon version (reproducing another old home remedy, a soothing honey-lemon tea). I’ve been using a knockoff version of the honey-lemon drops.
Then there are “natural” herbal remedies, in liquid or pill form. One brand:
From Napiers the Herbalists in Edinburgh: Lane’s Sage & Garlic Catarrh Remedy. Ingredients listed on the Napiers site:
Garlic is anti-bacterial, encourages perspiration and assists the expulsion of mucous. Red Sage [Salvia miltiorrhiza, used in traditional Chinese medicine] is antiseptic and astringent. Licorice encourages the expulsion of mucous.
And a more complex elixir:
Covonia contains boneset (Eupatorium perfoliatum, a common weed used by Native Americans to break fevers by inducing sweating) , blue flag (Iris versicolor, whose rhizomes yield a substance traditionally used, in small quatities, as a diuretic, liver purgative, and blood purifier), burdock root (species in the genus Arctium, whose roots are edible — Japanese gobo — and also yield an extract traditionally used to induce sweating and as a blood purifier) , and hyssop (Hyssopus officinalis, a bitter herb whose oil is traditionally used as an antiseptic, cough reliever, and expectorant).