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.
Entries linking to extension
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Original sense in English is obsolete.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.
Others are reading
they applied for an extension of the loan
extension of the program to all in need
most BASIC files use the filename extension .BAS
most applications provide extensions for the files they create
the extension of `satellite of Mars' is the set containing only Demos and Phobos
good extension comes from a combination of training and native ability
the dancer was praised for her uncanny extension
the wire has an extension of 50 feet