universal (adj.)

1580s, "the whole world, cosmos, the totality of existing things," from Old French univers (12c.), from Latin universum "all things, everybody, all people, the whole world," noun use of neuter of adjective universus "all together, all in one, whole, entire, relating to all," literally "turned into one," from unus "one" (from PIE root *oi-no- "one, unique") + versus, past participle of vertere "to turn, turn back, be turned; convert, transform, translate; be changed" (from PIE root *wer- (2) "to turn, bend").

Proto-Indo-European root meaning "one, unique."

It forms all or part of: a (1) indefinite article; alone; an; Angus; anon; atone; any; eleven; inch (n.1) "linear measure, one-twelfth of a foot;" lone; lonely; non-; none; null; once; one; ounce (n.1) unit of weight; quincunx; triune; unanimous; unary; une; uni-; Uniate; unilateral; uncial; unicorn; union; unique; unison; unite; unity; universal; universe; university; zollverein.

It is the hypothetical source of/evidence for its existence is provided by: Greek oinos "ace (on dice);" Latin unus "one;" Old Persian aivam; Old Church Slavonic -inu, ino-; Lithuanian vienas; Old Irish oin; Breton un "one;" Old English an, German ein, Gothic ains "one."