establish v.

mid-12c., "trustworthy, reliable;" mid-13c., "constant, steadfast; virtuous;" from Old French stable, estable "constant, steadfast, unchanging," from Latin stabilis "firm, steadfast, stable, fixed," figuratively "durable, unwavering," literally "able to stand," from PIE *stedhli-, suffixed form of root *sta- "to stand, make or be firm." From c. 1300 as "well-founded, well-established, secure" (of governments, etc.). Physical sense of "secure against falling" is recorded from late 14c.; also "of even temperament." Of nuclear isotopes, from 1904.

the later Romans evidently found words beginning in sc-, sp-, st- difficult or unpleasant to pronounce; in Late Latin forms begin to emerge in i- (such as ispatium, ispiritu), and from 5c. this shifted to e-. The development was carried into the Romanic languages, especially Old French, and the French words were modified further after 15c. by natural loss of -s- (the suppression being marked by an acute accent on the e-), while in other cases the word was formally corrected back to the Latin spelling (for example spécial). Hence French état for Old French estat for Latin status, etc. It also affected Romanic borrowings from Germanic (such as espy, eschew).

A different e- is a reduced form of Latin ex- before consonants (see ex-), and the e- in enough is an unfelt survival of an Old English alternative form of ge-.