Etymology
Advertisement
back down (v.)
in figurative sense of "withdraw a charge," 1859, American English, from notion of descending a ladder, etc. (the literal sense by 1849); from back (v.) + down (adv.).
Related entries & more 
Advertisement
spitball (n.)
1846 in the schoolboy sense, "bit of paper chewed and rounded as a missile;" 1904 in the baseball sense, from spit (n.1) + ball (n.1).
Related entries & more 
non-aligned (adj.)

also nonaligned, by 1960 in geopolitical sense, from non- + past participle of align. Non-alignment (also nonalignment) in this sense is attested from 1934.

Related entries & more 
chemistry (n.)

c. 1600, "alchemy," from chemist + -ry; also see chemical (adj.). The meaning "natural physical process" is from 1640s; the sense of "scientific study of the composition of material things and the changes they undergo" is by 1788. The figurative sense of "instinctual attraction or affinity" is attested slightly earlier, from the alchemical sense.

Related entries & more 
unblemished (adj.)
c. 1300, from un- (1) "not" + past participle of blemish (v.). Originally in moral sense; material sense is attested from mid-15c.
Related entries & more 
Advertisement
discovery (n.)

1550s (Hakluyt), "fact of discovering what was previously unknown;" see discover + -y (1). Earlier in this sense was discovering (mid-14c.). Meaning "that which is discovered" is from 1630s. Sense "act of revealing" (1580s) preserves the usual Middle English sense of discover but is now obsolete except in the legal sense of "disclosure by a party to an action" (of facts, documents, etc.), attested from 1715.

Related entries & more 
left wing (n.)
also (as an adjective) left-wing, 1871 in the political sense (1530s in a military formation sense), from left (adj.) + wing (n.). Related: Left-winger.
Related entries & more 
respectively (adv.)

mid-15c., respectiveli, "relatively" (a sense now obsolete); 1580s, "respectfully" (a sense now archaic); 1620s, "relatively to each of several singly," from respective (adj.) + -ly (2).

Related entries & more 
mine (v.2)
"lay explosives," 1620s, in reference to old tactic of tunneling under enemy fortifications to blow them up; a specialized sense of mine (v.1) via a sense of "dig under foundations to undermine them" (late 14c.), and miner in this sense is attested from late 13c. Related: Mined; mining.
Related entries & more 
disaffect (v.)

1620s, "lack affection for" (a sense now obsolete); 1640s, "alienate the affection of, make less friendly" (the main modern sense), from dis- + affect (v.1). Related: Disaffected; disaffecting.

Related entries & more 

Page 10