h₂ep-
“away from, off, above”above/off
PIE preposition meaning away from, off, or above. Source of Latin ab, English "off," and Greek apo.
Discussion
*h₂ep- is a Proto-Indo-European preposition and preverb meaning "away from," "off," or "above," one of the most common spatial morphemes in PIE.
Latin ab "from, away from" is the primary reflex, yielding English absent, absolve, abuse, and the prefix ab-. Greek apó "from, away" gives the prefix apo- in English (apology, apostle, apocalypse, apocryphal). Germanic *af gives Old English of/æf (modern English of, off), German ab "off," and the prefix after- in some compounds.
Sanskrit ápa "away, off" and Avestan apa confirm the Indo-Iranian branch. Hittite āppa "behind, back" preserves an archaic spatial sense.
The initial laryngeal *h₂ is reflected in the a-vocalism across branches. The semantic range encompasses separation (away from), removal (off), and elevation (above), with different daughter languages specializing in different senses.
Modern descendants include English of, off, the ab- prefix (absent, abstract, absorb), and through Greek: apo- (apology, apostle, apocalypse, apocryphal, apotheosis).
Notes
Source of Latin "ab" (from), English "of", "off", "above". Ablative spatial root.