Origins
The word 'up' is one of the most versatile in English, functioning as adverb, preposition, adjective, noun, and verb, and appearing in well over a hundred phrasal verbs.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ Its etymology connects it to a PIE root whose reflexes span opposite meanings β 'up' and 'under' β depending on which end of the vertical axis a language chose to emphasize.
It descends from Old English 'up' or 'Ε«p' (up, upward), from Proto-Germanic *up (up, upward), from PIE *upo (up from below, over). The PIE form contained two directional components: 'up' and 'from below.' Languages that emphasized the upward direction produced words meaning 'up' (Germanic *up). Languages that emphasized the 'from below' component produced words meaning 'under' (Greek 'hypΓ³,' Latin 'sub'). The same root, the same spatial concept, opposite resulting meanings β a striking illustration of how perspective shapes semantics.
Greek 'hypΓ³' (α½ΟΟ, under, from below, beneath) gave English the prefix 'hypo-': 'hypothermia' (under-heat, below normal temperature), 'hypothesis' (a placing under β a foundation for reasoning), 'hypodermic' (under the skin), and 'hypocrite' (one who plays a part underneath β an actor, one who speaks from behind a mask). Latin 'sub' (under, below, from below) β from PIE *upo with a prefixed *s- β gave 'submarine' (under the sea), 'subject' (thrown under), 'suburb' (under/near the city), 'subtle' (woven under β finely woven), and 'substance' (standing under β the foundation of a thing). Latin 'super' (over, above) β from *upo extended with *-per (over, through) β gave 'superior,' 'supreme,' 'superb,' and 'super.' All of these β 'up,' 'hypo-,' 'sub-,' 'super-' β trace to the single root *upo.
Proto-Indo-European Roots
German 'auf' (up, on, upon) is the direct cognate, showing a regular consonant shift. Dutch 'op' (up, on) and Swedish 'upp' (up) preserve the simpler Germanic form. The word 'open' is probably related β from Proto-Germanic *upanaz (opened up, raised) β suggesting that to open something was originally to lift it up.
In Modern English, 'up' is extraordinarily productive in phrasal verbs, where it adds a bewildering range of meanings: completion ('eat up,' 'use up,' 'drink up'), intensification ('speed up,' 'heat up'), creation ('make up,' 'build up'), destruction ('break up,' 'tear up,' 'blow up'), and beginning ('start up,' 'fire up'). The completive sense β 'finish up,' 'clean up,' 'wrap up' β is particularly puzzling to non-native speakers, as it has no obvious connection to vertical motion. It may derive from the metaphor of filling a vessel 'up' to the top, hence 'to completion.' This extraordinary polysemy makes 'up' one of the most challenging English words for language learners, despite being only two letters long.