Etymology
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attestation (n.)

mid-15c., attestacion, "testimony, a document embodying testimony," from Latin attestationem (nominative attestatio) "an attesting, testimony," noun of action from past-participle stem of attestari "to prove, confirm" (see attest). From 1670s as "a declaration in support of a fact."

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endorse (v.)

c. 1400, endosse "confirm or approve" (a charter, bill, etc.), originally by signing or writing on the back of the document, from Old French endosser (12c.), literally "to put on the back," from en- "put on" (see en- (1)) + dos "back," from Latin dossum, variant of dorsum "back" (see dorsal). Assimilated 16c. in form to Medieval Latin indorsare. Figurative sense of "confirm, approve" is recorded in English first in 1847. Related: Endorsed; endorsing.

You can endorse, literally, a cheque or other papers, &, metaphorically, a claim or argument, but to talk of endorsing material things other than papers is a solecism. [Fowler]
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firm (n.)
"business house," 1744, according to Barnhart from German Firma "a business, name of a business," originally "signature," from Italian firma "signature," from firmare "to sign," from Latin firmare "make firm, affirm," in Late Latin, "confirm (by signature)," from firmus "strong; stable," figuratively "constant, trusty" (see firm (adj.)).
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ratification (n.)

"act by which a competent authority gives sanction and validity to something done by another," mid-15c., ratificacion, from Old French ratification (14c.) and directly from Medieval Latin ratificationem (nominative ratificatio), noun of action from past-participle stem of ratificare "to confirm, approve" (see ratify).

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sanction (n.)

early 15c., "confirmation or enactment of a law," from Latin sanctionem (nominative sanctio) "act of decreeing or ordaining," also "decree, ordinance," noun of action from past-participle stem of sancire "to decree, confirm, ratify, make sacred" (see saint (n.)). Originally especially of ecclesiastical decrees.

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fasten (v.)
Old English fæstnian "make fast, make firm, fix, secure," also "ratify, betroth, confirm," from Proto-Germanic *fastinon "to make firm or fast" (source also of Old Frisian festnia "to make firm, bind fast," Old Saxon fastnon, Old High German fastnion, German festnen, Old Norse fastna "to pledge, betroth"), from PIE *fast "solid, firm" (see fast (adj.)). Related: Fastened; fastening.
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aver (v.)
late 14c., "assert the truth of," from Old French averer "verify, confirm, prove" (12c.), from Vulgar Latin *adverare "make true, prove to be true," from Latin ad "to" (see ad-) + verus "true" (from PIE root *were-o- "true, trustworthy"). From 1580s as "affirm with confidence." Related: Averred; averring.
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grant (n.)
late 14c., "something granted; authoritative bestowal of a privilege, etc.," from Anglo-French graunt, Old French graant, collateral variant of creant "promise, assurance, vow; agreement, pact; will, wish, pleasure," from creanter "be pleasing; assure, promise, guarantee; confirm, authorize" (see grant (v.)). Earlier in English in now-obsolete sense of "allowance, permission" (c. 1200). Especially "money formally granted by an authority" from c. 1800. In American English, especially of land, from c. 1700.
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adjure (v.)

late 14c., adjuren, "to bind by oath; to question under oath;" c. 1400 as "to charge with an oath or under penalty of a curse," from Latin adiurare "confirm by oath, add an oath, to swear to in addition; call to witness," in Late Latin "to put (someone) to an oath," from ad "to" (see ad-) + iurare "swear," from ius (genitive iuris) "law" (see jurist). Related: Adjured; adjuring.

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corroborate (v.)

1520s, "to give (legal) confirmation to," from Latin corroboratus, past participle of corroborare "to strengthen, invigorate," from assimilated form of com "with, together," here perhaps "thoroughly" (see com-) + roborare "to make strong," from robur, robus "strength," (see robust).

Meaning "to strengthen by evidence, to confirm" is from 1706. Sometimes 16c.-18c. in its literal Latin sense "make strong or add strength to," especially of medicines. Related: Corroborated; corroborating; corroborative.

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