Latin 'versus' (turned toward) — two parties 'versus' each other are literally turned to face off.
Against; in contrast to; as opposed to. Used to indicate opposition between two sides, especially in legal cases and competitions.
Directly from Latin 'versus' (turned toward, turned against, in the direction of), the past participle of 'vertere' (to turn, to change direction), from PIE *wert- (to turn, to wind, to rotate). The PIE root *wert- is among the most generative in Indo-European: Sanskrit 'vartate' (turns, revolves), Avestan 'varəta' (turned), Lithuanian 'versti' (to overturn), Old Norse 'verða' (to become, to happen), German 'werden' (to become), Old English 'weorþan' (to become — the origin of 'worth' in the sense of what something is turning into or is valued at). Latin 'vertere' produced an enormous family: 'versūs' (a line of verse — the turning of the plough at the end of the furrow, then the turning of the writing stylus), 'universus' (turned into one — universe), 'diversus' (turned apart —
The abbreviation 'vs.' (or 'v.' in British legal usage) has become so common that many English speakers do not realize 'versus' is a Latin word at all. In American pop culture, 'vs.' has extended far beyond legal and sporting contexts — movie titles like 'Alien vs. Predator' and debates like 'cats vs. dogs' show how thoroughly the Latin preposition has been naturalized into colloquial English.