Old English streaw (rare) "stems or stalks of certain species of grains," apparently literally "that which is scattered or strewn," related to streowian (see strew), from Proto-Germanic *straw- "that which is scattered" (source also of Old Norse stra, Danish straa, Swedish strå, Old Saxon stro, Old Frisian stre, Old Dutch, Old High German stro, Dutch stroo, German Stroh "straw"), from PIE root *stere- "to spread." The notion perhaps is of dried grain stalks strewn on a floor as carpeting or bedding.
As a type of what is trifling or unimportant, attested from late 13c. Meaning "hollow tube through which a drink is sucked" is recorded from 1851. To draw straws as a means of deciding something is recorded from 1779 (the custom probably is older). As an adjective, "made of straw," mid-15c.; hence "false, sham." Straw poll is from 1932; earlier straw vote (1866). Straw hat first attested mid-15c. To clutch (or grasp or catch) at straws (1748) is what a drowning man proverbially would do. The last straw (1836 apart from the full phrase) is from the proverbial image: "it is the last straw that breaks the camel's back" (or, less often, the mare's, the horse's, or the elephant's), an image in use in English by 1755.
Let it not, however, be inferred that taxation cannot be pushed too far : it is, as the Oriental proverb says, the last straw that overloads the camel ; a small addition, if ill-timed, may overturn the whole. [The Scots Magazine, April 1799]
It forms all or part of: consternate; consternation; construct; construction; destroy; destruction; industry; instruct; instruction; instrument; obstruct; obstruction; perestroika; prostrate; sternum; sternocleidomastoid; strain (n.2) "race, stock, line;" stratagem; strategy; strath; strato-; stratocracy; stratography; stratosphere; stratum; stratus; straw; stray; street; strew; stroma; structure; substrate; substratum; substructure.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit strnoti "strews, throws down;" Avestan star- "to spread out, stretch out;" Greek stronymi "strew," stroma "bedding, mattress," sternon "breast, breastbone;" Latin sternere "to stretch, extend;" Old Church Slavonic stira, streti "spread," strana "area, region, country;" Russian stroji "order;" Gothic straujan, Old High German strouwen, Old English streowian "to sprinkle, strew;" Old English streon "strain," streaw "straw, that which is scattered;" Old High German stirna "forehead," strala "arrow, lightning bolt;" Old Irish fo-sernaim "spread out," srath "a wide river valley;" Welsh srat "plain."
"mattress," late 14c., paillet "bed or mattress of straw; small, simple bed," from Anglo-French paillete "straw, bundle of straw," Old French paillet "chaff, bundle of straw," from paille "straw" (12c.), from Latin palea "chaff," perhaps from PIE *pelh- "chaff," source also of Sanskrit palavah "chaff, husk," Old Church Slavonic plevy, Russian polova "chaff," Lithuanian pelūs "chaff."
1510s, "teacher's pointer," alteration of festu "piece of straw, twig" (late 14c.), from Old French festu "straw; object of little value" (12c., Modern French fétu), from Vulgar Latin *festucum, from Latin festuca "straw, stalk, rod," probably related to ferula "reed, whip, rod" (see ferule). Sense of "pasture, lawn grass" is first recorded 1762. Wyclif (1382) has festu in Matthew vii.3 for the "mote" in the eye. In Old French rompre le festu was to symbolically break a straw to signify the breaking of a bond.