1530s, "a cleaning out, removal, clearance," from rid + -ance. The meaning "a deliverance from something superfluous or unwanted" is from 1590s. Good riddance, "a welcome relief from unpleasant company or an embarrassing connection" attested from 1650s. Shakespeare has gentle riddance (1590s); Middleton has fair riddance (1610s).

late 14c., respiren, "breathe, draw breath," from Old French respirer (12c.) and directly from Latin respirare "breathe again, breathe in and out," from re- "again" (see re-) + spirare "to breathe" (see spirit (n.)). Formerly also "to rest or enjoy relief after toil or exertion" (1590s). Related: Respired; respiring.

early 15c., "mitigation, relief," from Medieval Latin alleviationem (nominative alleviatio), noun of action from past-participle stem of alleviare "lift up, raise," figuratively "to lighten (a burden), comfort, console," from assimilated form of Latin ad "to" (see ad-) + levis "light" in weight (from PIE root *legwh- "not heavy, having little weight").

late 14c., "relief from misfortune," see discharge (v.). Meaning "release from work or duty" is from early 15c. Meaning "act of sending out or pouring forth" is from c. 1600; sense of "that which is emitted or poured forth" is from 1727. Meaning "action of firing off a firearm or other missile weapon" is from 1590s. Electricity sense is from 1794. 

1550s, originally in mathematics, from converse (adj.). From 1786 as "thing or action that is the exact opposite of another." As an example, Century Dictionary gives "the hollows in a mold in which a medal has been cast are the converse of the parts of the medal in relief." Chaucer has in convers, apparently meaning "on the other side."

late 14c., "the art or process of sculpture, the act or art of carving or shaping figures and other objects in the round or in relief on more or less hard surfaces," from Latin sculptura "sculpture," from past participle stem of sculpere "to carve, engrave," a back-formation from compounds such as exculpere, from scalpere "to carve, cut" (from PIE root *skel- (1) "to cut"). The meaning "a work of carved art" is from 1610s.

1823, "pertaining to health or hygiene," from French sanitaire (1812), from Latin sanitas "health," from sanus "healthy; sane" (see sane). In reference to menstrual devices, by 1881 (in sanitary towel). In U.S. history the Sanitary Commission, created by the Secretary of War in 1861, provided relief to soldiers and oversaw military lodging and hospitals. Sanitarian is by 1859 as "promoter of, or one versed in, sanitary measures or reforms;" sanitarist in that sense also is by 1859.