double standard n.

c. 1300, "twice as much or as large," also "repeated, occurring twice," also "of extra weight, thickness, size, or strength; of two layers," from Old French doble (10c.) "double, two-fold; two-faced, deceitful," from Latin duplus "twofold, twice as much," from duo "two" (from PIE root *dwo- "two") + -plus "more" (see -plus).

From early 14c. as "having a twofold character or relation," also "consisting of two in a set together; being a pair, coupled." From mid-14c. as "characterized by duplicity." The earliest recorded use in English is c. 1200, in double-feast "important Church festival."

Double-chinned is from late 14c.; double-jointed, of persons, is by 1828. Military double time (1833) originally was 130 steps per minute; double quick (adj.) "very quick, hurried" (1822) originally was military, "performed at double time."

The photographic double exposure is by 1872. The cinematic double feature is by 1916. Double figures "numbers that must be represented numerically by two figures" is by 1833. Double-vision is by 1714. Double indemnity in insurance is by 1832; double jeopardy is by 1817. The baseball double play is by 1866.

Double trouble "twice the trouble" is by 1520s; in 19c. America it was the name of a characteristic step of a rustic dance or breakdown, derived from slave dancing on plantations. A double-dip (n.) originally was an ice-cream cone made with two scoops (1936); the figurative sense is by 1940. Double bed "bed made to sleep two persons" is by 1779. Double life "a sustaining of two different characters in life" (typically one virtuous or respectable, the other not) is by 1888.

mid-12c., "flag or other conspicuous object to serve as a rallying point for a military force," from shortened form of Old French estandart "military standard, banner." According to Barnhart, Watkins and others, this is probably from Frankish *standhard, literally "stand fast or firm," a compound of unrecorded Frankish words cognate stand (v.) and hard (adj.). So called because the flag was fixed to a pole or spear and stuck in the ground to stand upright. The other theory [OED, etc.] calls this folk-etymology and connects the Old French word to estendre "to stretch out," from Latin extendere (see extend). Some senses (such as "upright pole," mid-15c.) seem to be influenced by if not from stand (v.). Standard-bearer in the figurative sense is from 1560s.