word-forming element meaning "together, with," sometimes merely intensive; it is the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations (such as costar), co- tends to be used where Latin would use con-.

late 13c., "last will disposing of property," from Latin testamentum "a last will, publication of a will," from testari "make a will, be witness to," from testis "witness," from PIE *tri-st-i- "third person standing by," from root *tris- "three" (see three) on the notion of "third person, disinterested witness."

Use in reference to the two divisions of the Bible (early 14c.) is from Late Latin vetus testamentum and novum testamentum, loan-translations of Greek palaia diatheke and kaine diatheke. Late Latin testamentum in this case was a confusion of the two meanings of Greek diatheke, which meant both "covenant, dispensation" and "will, testament," and was used in the former sense in the account of the Last Supper (see testimony) but subsequently was interpreted as Christ's "last will."

"disputed, made the object of contention or competition," 1670s, past-participle adjective from contest (v.). Specifically of elections from 1771, American English.

"one who contests, a disputant, a litigant," 1660s, from contestant (adj.), 1660s, from French contestant, present participle of contester (see contest (v.)). Revived and popularized 1861, when it became a journalist's term for the combatants on either side in the U.S. Civil War.

1540s, "action of calling to witness," from Latin contestationem (nominative contestatio), "an attesting, testimony," noun of action from past-participle stem of contestari (see contest (v.)). Meaning "disputation, controversy" is from 1570s.

"not admitting of dispute or debate, too clear to be controverted," 1670s, from in- "not" (see in- (1)) + contestable (see contest (v.)). Perhaps from or modeled on French incontestable. Related: Incontestably.