early 15c., "quality of rashness or heedlessness; imprudent act," from Old French imprudence (14c.) or directly from Latin imprudentia "lack of foresight, inconsiderateness, ignorance, inadvertence," abstract noun from imprudens "unaware, inconsiderate" (see imprudent).
mid-14c., "want of discretion, imprudence," from Old French indiscrecion "foolishness, imprudence" (12c.), from Late Latin indiscretionem (nominative indiscretio) "lack of discernment," from in- "not, opposite of" (see in- (1)) + discretionem "discernment, power to make distinctions" (see discretion). Meaning "indiscreet act" is from c. 1600.
mid-15c., "a scraping instrument;" late 15c., "act of scraping or scratching," from scrape (v.). By 1886 as "a scraping sound."
From 1620s as a type of awkward bow or gesture of obeisance, in which the foot is drawn, or "scraped," backward. The meaning "embarrassing or awkward predicament," usually due to imprudence or thoughtlessness, is by 1709, as OED suggests, probably "from the notion of being 'scraped' in going through a narrow passage." In old slang it could mean "a shave" (1859).