early 15c., pois, "weight, quality of being heavy," later "significance, importance" (mid-15c.), from Old French pois "weight, balance, consideration" (12c., Modern French poids, with -d- added 16c. on supposed derivation from Latin pondus "weight"), from Medieval Latin pesum "weight," from Latin pensum "something weighted or weighed," (source of Provençal and Catalan pes, Spanish, Portuguese, Italian peso), noun use of neuter past participle of pendere "to hang, cause to hang; weigh" (from PIE root *(s)pen- "to draw, stretch, spin").
Original senses are obsolete. The figurative sense (in reference to abstract things) of "steadiness, balance, equilibrium, composure" is recorded from 1640s, from the sense of "a state of of being equally weighted on either side" (1550s). The meaning "way in which the body is carried" is from 1770.
late 14c., poisen, "to have (a specified) weight," a sense now obsolete, from Old French poiser, stressed form of peser "to weigh, be heavy; weigh down, be a burden; worry, be a concern," from Vulgar Latin *pesare, from Latin pensare "to weigh carefully, weigh out, counter-balance," frequentative of pendere (past participle pensus) "to hang, cause to hang; weigh; pay" (from PIE root *(s)pen- "to draw, stretch, spin").
The meaning "to weigh, ascertain by weighing or balancing is from 1590s, hence the meaning "to hold or place in equilibrium or balance," from 1630s (compare equipoise). The intransitive sense of "be balanced or suspended," figuratively "to hang in suspense" is by 1847; the passive sense of "to be ready" (for or to do something) is by 1932. Related: Poised; poising. In 15c. a poiser was an official who weighed goods. The secondary sense of "to ponder, consider" in Latin pensare yielded pensive; that sense was occasional, but rare in Middle English poise.
Proto-Indo-European root meaning "to draw, stretch, spin."
It forms all or part of: append; appendix; avoirdupois; compendium; compensate; compensation; counterpoise; depend; dispense; equipoise; expend; expense; expensive; hydroponics; impend; painter (n.2) "rope or chain that holds an anchor to a ship's side;" pansy; penchant; pend; pendant; pendentive; pending; pendular; pendulous; pendulum; pension; pensive; penthouse; perpendicular; peso; poise; ponder; ponderous; pound (n.1) "measure of weight;" prepend; prepense; preponderate; propensity; recompense; span (n.1) "distance between two objects;" span (n.2) "two animals driven together;" spangle; spanner; spend; spider; spin; spindle; spinner; spinster; stipend; suspend; suspension.
It is the hypothetical source of/evidence for its existence is provided by: Latin pendere "to hang, to cause to hang," pondus "weight" (perhaps the notion is the weight of a thing measured by how much it stretches a cord), pensare "to weigh, consider;" Greek ponos "toil," ponein "to toil;" Lithuanian spendžiu, spęsti "lay a snare;" Old Church Slavonic peti "stretch, strain," pato "fetter," pina "I span;" Old English spinnan "to spin," spannan "to join, fasten; stretch, span;" Armenian henum "I weave;" Greek patos "garment," literally "that which is spun;" Lithuanian pinu "I plait, braid," spandau "I spin;" Middle Welsh cy-ffiniden "spider;" Old English spinnan "draw out and twist fibers into thread," spiðra "spider," literally "spinner."
mid-14c., ponderen, "to estimate the worth of, to appraise" (a sense now obsolete), from Old French ponderer "to weigh, poise" (14c., Modern French pondérer) and directly from Latin ponderare "ponder, consider, reflect," literally "to weigh," from pondus (genitive ponderis) "weight," from stem of pendere "to hang, cause to hang; weigh" (from PIE root *(s)pen- "to draw, stretch, spin"). Meaning "to judge (a matter or action) mentally, weigh carefully in the mind" is attested from late 14c. Related: Pondered; pondering; ponderation (1550s in the mental sense).
also dumbbell, "one of a pair of weighted bars used for exercise," by 1785, earlier (from 1711), according to OED, an apparatus like that used to ring a church bell, but without the bell (hence dumb); used for physical exercise but sometimes also to practice ringing changes. See dumb (adj.) + bell (n.). If this is right, the word must have been transferred; earlier 18c. references make mention of "pulling" or "ringing" dumb-bells and note that it can be done only indoors. The following is a footnote to the 1903 reprint of Joseph Strutt's 1801 "The Sports and Pastimes of the People of England":
The origin of the term is somewhat curious. Dumb-bells take their name by analogy, as was pointed out in Notes and Queries in 1861, "from a machine used for exercise, consisting of a rough, heavy, wooden flywheel with a rope passing through and round a spindle ... and set in motion like a church bell." This statement, however, does not sufficiently explain the transference of such a name to the short bar and rounded lead or iron ends of a hand dumb-bell. This difficulty was explained by the late Chancellor Ferguson in a paper read before the Archaeological Institute in 1895, wherein a dumb-bell apparatus, now at Lord Sackville's seat at Knowle, was described and illustrated. The roller round which the rope winds and unwinds has four iron arms, each of which has a leaden poise or ball at the end, just like the end of an ordinary hand dumb-bell. This Knowle example is fixed in an attic and the rope passed through to a gallery beneath. Anyone pulling the rope would get much the same exercise as in pulling a bell rope in a church tower, but without annoying his neighbours by the noise. There used to be a similar apparatus at New College, Oxford.
Figurative sense of "blockhead, stupid person" attested by 1918, American English college slang.