c. 1600, "under misapprehension, having made a mistake," past-participle adjective from mistake (v.). Meaning "misunderstood" is from 1590s; that of "erroneous, incorrect" is from 1670s. Related: Mistakenly. Mistaken identity in criminal cases is attested by 1838.
"to make naked," mid-14c., naken, from naked, perhaps with misapprehension of the -d as a past tense suffix. Marked as "Obs[olete] exc[ept] Sc[ottish]" in OED. Earlier was naken "to strip naked" (mid-13c.); a later generation coined nakedize (1858).
1540s, "having a conscience;" 1580s, of actions, "consonant with right or duty;" 1640s, of persons, "governed by conscience." It and conscioned "appear to be popular formations from conscion, taken as a singular of conscien-ce" by misapprehension of the "s" sound as a plural inflection [OED]. See conscience. Related: Conscionably. Obsolete from early 18c. but fossilized in its negative, unconscionable.
Better remembered, if at all, as a political term: During a heated Democratic party meeting in Tammany Hall c. 1835, the opposition doused the gaslights to break it up, and the radical delegates used loco-foco matches to relight them. When it was publicized, the name loco-foco entered U.S. political jargon (by 1837) and down to the Civil War was applied, usually disparagingly, to a radical faction of the Democratic Party (but by the Whigs to all Democrats).