early 15c., "fixed standard of measure" (surname Gageman is early 14c.), from Old North French gauge "gauging rod" (see gauge (v.)). Meaning "instrument for measuring" is from 1670s; meaning "distance between rails on a railway" is from 1841.
Railway-gage, the distance between perpendiculars on the insides of the heads of the two rails of a track. Standard gage is 4 feet 8 1/2 inches; anything less than this is narrow gage; anything broader is broad gage. The dimension was fixed for the United States by the wheels of the British locomotive imported from the Stephenson Works in 1829. [Century Dictionary]
"pointed pin of wood, metal, or other material," mid-15c., pegge, from Middle Dutch pegge "peg," or a similar Low German word (Low German pigge "peg," German Pegel "gauge rod, watermark," Middle Dutch pegel "little knob used as a mark," Dutch peil "gauge, watermark, standard"); of uncertain origin; perhaps from PIE *bak- "staff used as support" (see bacillus).
To be a square peg in a round hole (or the reverse) "be inappropriate for one's situation" is attested by 1836; to take someone down a peg "humble, lower the esteem of" is from 1580s, but the original literal sense is uncertain (most of the sensibly plausible candidates are not attested until centuries later). Peg leg "wooden leg of the simplest form" is attested from 1765.
The meaning "pattern or gauge for shaping a piece of work" is first recorded 1819 in this form, earlier temple (1680s); the form was altered mid-19c., probably influenced by plate [Barnhart], but the pronunciation did not begin to shift until more recently (templet is still the primary entry for the word in Century Dictionary).
Middle English narwe, from Old English nearu "of little width, not wide or broad; constricted, limited; petty; causing difficulty, oppressive; strict, severe," from West Germanic *narwaz "narrowness" (source also of Frisian nar, Old Saxon naru, Middle Dutch nare, Dutch naar) which is not found in other Germanic languages and is of unknown origin.
In reference to railroads, narrow-gauge (also narrow-gage) is by 1841, originally of those less than the standard of 4 feet 8 1/2 inches. The narrow seas (mid-15c.) were the waters between Great Britain and the continent and Ireland, but specifically the Strait of Dover.
late 14c., ajusten, "to correct, remedy," from Old French ajuster, ajoster "add; assemble; calibrate, gauge, regulate," from Late Latin adiuxtare "to bring near," from ad "to" (see ad-) + Latin iuxta "next, close by," from suffixed form of PIE root *yeug- "to join."
In 16c. French corrected to adjuster, but the pedantic effort was rejected and Modern French has ajouter. Influenced in form and sense by folk-etymology, as if from ad- + iustus "just, equitable, fair." English reborrowed the word by c. 1600 in sense "arrange, settle, compose," from French adjuster "fit (things together) properly, put things in order." Meaning "to arrange (something) so as to conform with (a standard or another thing)" is from 1660s. Insurance sense is from 1755 (see adjuster). To adjust to "get used to" is attested by 1924. Related: Adjusted; adjusting.
c. 1300, sauf, "unscathed, unhurt, uninjured; free from danger or molestation, in safety, secure; saved spiritually, redeemed, not damned;" from Old French sauf "protected, watched-over; assured of salvation," from Latin salvus "uninjured, in good health, safe," which is related to salus "good health," saluber "healthful" (all from PIE *solwos from root *sol- "whole, well-kept"). For the phonological development of safe from sauf, OED compares gage from Old North French gauge.
From late 14c. as "rescued, delivered; protected; left alive, unkilled." The meaning "not exposed to danger" (of places, later of valuables) is attested from late 14c.; in reference to actions, etc., the meaning "free from risk," is recorded by 1580s. The sense of "sure, reliable, not a danger" is from c. 1600. The sense of "conservative, cautious" is from 1823. It has been paired alliteratively with sound (adj.) from c. 1300. In Middle English it also meant "in good health," also "delivered from sin or damnation." Related: Safeness.