early 15c., indenten, endenten "to make notches; to give (something) a toothed or jagged appearance," also "to make a legal indenture, make a written formal agreement or contract," from Old French endenter "to notch or dent, give a serrated edge to" (12c.) and directly from Medieval Latin indentare "to furnish with teeth," from in- "into, in, on, upon" (from PIE root *en "in") + verb from Latin dens (genitive dentis) "tooth" (from PIE root *dent- "tooth").
An indented document was usually, if not always, written in two or more identical versions. Orig. these were written on a single sheet of parchment and then cut apart along a zigzag, or 'indented' line. Each party to the agreement retained one copy, which he could readily authenticate by matching its serrate edge with that of another copy. [Middle English Compendium]
The printing sense "insert white space to force text inward" is first attested 1670s. Related: Indented (late 14c.); indenting.
Such contracts (especially between master craftsmen and apprentices) were written in full identical versions on a sheet of parchment, which was then cut apart in a zigzag, or "notched" line. Each party took one, and the genuineness of a document of indenture could be proved by laying it beside its counterpart.
Proto-Indo-European root meaning "tooth."
It forms all or part of: al dente; dandelion; dental; dentifrice; dentist; dentition; denture; glyptodon; indent (v.1) "to make notches;" mastodon; orthodontia; periodontal; teethe; tooth; toothsome; tusk; trident.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit danta, Greek odontos (gen.), Latin dens, Lithuanian dantis, Old Irish det, Welsh dent, Old English toð, German Zahn, Gothic tunþus "tooth."
late 14c., "have a strong effect on the mind or heart, to stamp deeply in the mind," from Latin impressus, past participle of imprimere "press into or upon, stamp," also figurative, from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + premere "to press, hold fast, cover, crowd, compress" (from PIE root *per- (4) "to strike"). Literal sense of "to apply with pressure, make a permanent image in, indent, imprint" is from early 15c. in English. Related: Impressed; impressing.