early 14c., "to value, assess," from Anglo-French estendre (late 13c.), Old French estendre "stretch out, extend, increase," transitive and intransitive (Modern French étendre), from Latin extendere "stretch out, spread out; increase, enlarge, prolong, continue," from ex "out" (see ex-) + tendere "to stretch," from PIE root *ten- "to stretch."
Original sense in English is obsolete. From late 14c. as "lengthen or extend in time," also "straighten" (an arm, wing. etc.). Meaning "make longer and/or broader in space" is from early 15c., as is intransitive sense of "cover an area, have a certain extent in space;" sense of "expand, grow distended" is from 1753. Related: Extended; extending.
"one who or that which extends or stretches," 1610s, agent noun from extend (v.). Middle English had extendour "surveyor, assessor."
"capable of being extended," 1610s, from French extensible, from stem of Latin extendere "to spread out" (see extend). Earlier was extendible (late 15c.).
"vast, far-reaching;" c. 1600 of immaterial, c. 1700 of material things; from Late Latin extensivus, from extens-, past-participle stem of Latin extendere "to stretch out, spread" (see extend). Earlier in a medical sense, "characterized by swelling" (early 15c.). Related: Extensively; extensiveness.
c. 1300, extente, "tax levied on value; value of property for taxation," from Anglo-French extente, estente "extent, extension;" in law, "valuation of land, stretch of land," from fem. past participle of Old French extendre "extend," from Latin extendere "to spread out, spread" (see extend). Meaning "degree to which something extends" is from 1590s.
c. 1400, "swelling, bulging," from Latin extensionem/extentionem (nominative extensio/extentio) "a stretching out, extension," noun of action from past-participle stem of extendere (see extend). In a concrete sense, "extended portion of something" (a railroad, etc.), from 1852. Telephone sense is from 1906.
mid-15c., "occupying time, made longer," past-participle adjective from extend (v.). Meaning "stretched out" in space is from 1550s; extended-play (adj.), in reference to recordings (especially 7-inch, 45 rpm vinyl records) is from 1953; in reference to pinball games by 1943. Extended family (n.) in sociology recorded from 1942.
A challenging question was asked RCA engineers and scientists in 1951. How can we increase the playing time of a 7-inch record, without using a larger disc? Sixteen months of research gave the answer, "45 EP"—Extended Play. [Radio Corporation of America magazine advertisement, May 1953]