late 14c., "contaminating or contaminated, containing contagion" (of air, water, etc.); "communicable" (of disease); also "morally corrupting," from Old French contagieus (Modern French contagieux) and directly from Late Latin contagiosus, from Latin contagio "a touching, contact," often in a bad sense, "a contact with something physically or morally unclean, contagion," from contingere "to touch," from assimilated form of com "with, together" (see con-) + tangere "to touch," from PIE root *tag- "to touch, handle." Figuratively applied to anything apt to spread from one to another (rumor, etc.) from 1650s. Related: Contagiously; contagiousness.
"German measles," contagious disease characterized by rose-colored eruptions, 1883, Modern Latin, literally "rash," from noun use of neuter plural of Latin rubellus "reddish," diminutive of ruber "red" (from PIE root *reudh- "red, ruddy.").
c. 1300, "any infectious or contagious disease, fatal epidemic," from Old French pestilence "plague, epidemic" (12c.) and directly from Latin pestilentia "a plague, an unwholesome atmosphere," noun of condition from pestilentem (nominative pestilens) "infected, unwholesome, noxious," from pestis "deadly disease, plague" (see pest).
Also in Middle English "wickedness, evil, sin, a vice, that which is morally pestilential."
"chronic non-contagious skin disease characterized by dry, red patches covered with flakes," 1680s, from medical Latin psoriasis, in Late Latin "mange, scurvy," from Greek psōriasis "the itch; a being itchy," from psōrian "to have the itch," from psōra "itch, mange, scab," related to psēn "to rub" (see psilo-). Related: Psoriatic.
late 14c., "contaminated with dangerous disease; deadly, poisonous," from Latin pestilentem (nominative pestilens) "infected, unhealthy," from pestilis "of the nature of a plague," from pestis "deadly contagious disease" (see pest (n.)). Transferred sense of "mischievous, pernicious, hurtful to health or morals" is from 1510s; weakened sense of "troublesome" is from 1590s. Related: Pestilently.
1550s (in imprecations, "a pest upon ____," etc.), "plague, pestilence, epidemic disease," from French peste (1530s), from Latin pestis "deadly contagious disease; a curse, bane," a word of uncertain origin. Meaning "any noxious, destructive, or troublesome person or thing" is attested by c. 1600. Pest-house "hospital for persons suffering from infectious diseases" is from 1610s.
type of contagious disease characterized by inflammation of the glands, c. 1600, from plural of mump "a grimace" (1590s), originally a verb, "to whine or mutter like a beggar" (1580s), from Dutch mompen "to cheat, deceive," originally probably "to mumble, whine" and of imitative origin (compare mum (interj.), mumble). The infectious disease probably was so called in reference to swelling of the salivary glands of the face and/or to painful difficulty swallowing. Mumps also was used from 17c. to mean "a fit of melancholy, sullenness, silent displeasure."