1881, as a biochemical term, from German Enzym, coined 1878 by German physiologist Wilhelm Kühne (1837-1900), from Modern Greek enzymos "leavened," from en "in" (see en- (2)) + zymē "leaven" (see zymurgy). Related: Enzymotic.

"the black liquor with which men write" [Johnson], mid-13c., inke, from Old French enche, encre "dark writing fluid" (12c.), earlier enque (11c.), originally enca, from a shortening of Late Latin encaustum, from Late Greek enkauston. This is the neuter of the past-participle adjective enkaustos "burned in," from the stem of enkaiein "to burn in," from en- "in" (see en- (1)) + kaiein "to burn" (see caustic).

In Pliny the word is the name of a kind of painting method involving fire or heat.

It denoted a kind of painting practised by the ancients, in which the crayon was dipped in wax of various colours. Encausto pingere is to practise this art, paint in encaustic or enamel. [footnote in "The Life, Letters, and Sermons of Bishop Herbert de Losinga," Oxford, 1878]

Later it was the special name of the purple-red ink, the sacrum encaustum, used by the Roman emperors to sign their documents; this was said to have been obtained from the ground remains of certain shellfish, formed into writing fluid by the application of fire or heat, which explained the name. In the Code of Justinian, the making of it for common uses, or by common persons, was prohibited under penalty of death and confiscation of goods.

The usual word for "ink" in Latin was atramentum (source of Old French arrement), literally "anything that serves to dye black," from ater "black;" the Greek word was melan, neuter of melas "black." The Old English word for it was blæc, literally "black," and compare Swedish bläck, Danish blæk "ink." Spanish and Portuguese (tinta) and German (tinte) get their "ink" words from Latin tinctus "a dyeing."

Donkin credits a Greek pronunciation, with the accent at the front of the word, for the French evolution; the same Latin word, behaving regularly, became inchiostro (with unetymological -r-) in Italian, encausto in Spanish.

As an adjective, inken (c. 1600) occasionally has been used. Ink-slinger, contemptuous for "journalist," is from 1870. The psychologist's ink-blot test attested from 1915.

1550s, "engagement to marry," a variant of ensurance "an assurance, pledge, guarantee," from Old French enseurance "assurance," from ensurer, from en- "make" (see en- (1)) + sur "safe, secure, undoubted" (see sure (adj.)).

Commercial sense of "security against loss or death in exchange for payment" is from 1650s. Assurance was the older word for this specific sense (late 16c.). Compare insure.

also re-enforce, "add new force, strength, or weight to," c. 1600, originally in military sense, from re- "again" + inforce, variant of enforce "drive by physical force; fortify, strengthen" (compare re-enforce, and see en- (1)). Related: Reinforced; reinforcing.

The ordinary form ( rein-) has been so far divorced from the simple verb (formerly inforce or enforce, now always the latter) that it seldom or never means to enforce again, as when a lapsed regulation  is revived. For that sense re-enforce should be used. [Fowler]

Proto-Indo-European root meaning "in."

It forms all or part of: and; atoll; dysentery; embargo; embarrass; embryo; empire; employ; en- (1) "in; into;" en- (2) "near, at, in, on, within;" enclave; endo-; enema; engine; enoptomancy; enter; enteric; enteritis; entero-; entice; ento-; entrails; envoy; envy; episode; esoteric; imbroglio; immolate; immure; impede; impend; impetus; important; impostor; impresario; impromptu; in; in- (2) "into, in, on, upon;" inchoate; incite; increase; inculcate; incumbent; industry; indigence; inflict; ingenuous; ingest; inly; inmost; inn; innate; inner; innuendo; inoculate; insignia; instant; intaglio; inter-; interim; interior; intern; internal; intestine; intimate (adj.) "closely acquainted, very familiar;" intra-; intricate; intrinsic; intro-; introduce; introduction; introit; introspect; invert; mesentery.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit antara- "interior;" Greek en "in," eis "into," endon "within;" Latin in "in, into," intro "inward," intra "inside, within;" Old Irish in, Welsh yn, Old Church Slavonic on-, Old English in "in, into," inne "within, inside."

word-forming element meaning "put in or into, bring to a certain state," sometimes intensive, from French assimilation of en- "in, into" (see en- (1)) to following labial stop (-b-, -p-, and often -m-), or from the same development in later Latin in- (to im-). "This rule was not fully established in spelling before the 17th c." [OED], but it is likely the pronunciation shift was in Old French and Middle English and spelling was slow to conform. Also a living prefix in English used to form verbs from adjectives and nouns (embitter, embody). In words such as emancipate, emerge, emit, emotion the e- is a reduced form of Latin ex- (see ex-) before -m-.

before vowels encephal-, word-forming element meaning "brain, of the brain," from combining form of medical Latin encephalon, from Greek enkephalos "the brain," literally "within the head," from en "in" (see en- (2)) + kephalē "head" (see cephalo-).