"coffee-room, viewed from the inside through a glass door, as it was seen by Dickens on a dark London day; ... used by Chesterton to denote the queerness of things that have become trite, when they are seen suddenly from a new angle." [J.R.R. Tolkien, "On Fairy Stories"]
"apparent displacement of an object observed, due to an actual displacement of the observer," 1570s, from French parallaxe (mid-16c.), from Greek parallaxis "change, alteration, inclination of two lines meeting at an angle," from parallassein "to alter, make things alternate," from para- (see para- (1)) + allassein "to change," from allos "other" (from PIE root *al- "beyond"). Related: Parallactic.
in geology, "leaning against," as one stratum of rock against another, both turned up at an angle, 1837, from Latin acclinis "leaning on or against," related to acclinare "to lean on or against," from assimilated form of ad "to, upon" (see ad-) + clinare "to bend" (from PIE *klein-, suffixed form of root *klei- "to lean").
"short cannon, ordnance piece short in proportion to the size of its bore," fired at a high angle and meant to secure a vertical fall of the projectile, 1620s, originally mortar-piece (1550s), from French mortier "short cannon," in Old French, "bowl for mixing or pounding" (see mortar (n.2)). So called for its shape.
"act of bending the knee," especially in worship, early 15c., genu-fleccion, from Medieval Latin genuflectionem (nominative genuflexio) "bending of the knee," noun of action from past-participle stem of Late Latin genuflectere "genuflect," properly genu flectere "to bend the knee," from Latin genu "knee" (from PIE root *genu- (1) "knee; angle") + flectere "to bend" (see flexible).
It forms all or part of: hacek; hack (v.1) "to cut roughly, cut with chopping blows;" hake; Hakenkreuz; heckle; hook; hooker.
It is the hypothetical source of/evidence for its existence is provided by: Russian kogot "claw;" Old English hoc "hook, angle."