Other forms: vouched, vouching, vouches
To vouch for somebody is to state that you can answer for their honesty. Vouch for him, I can vouch for that, nobody would vouch for her.
The preposition is for, and vouching commits your own reputation to somebody else's — which is why people are careful about it. You can also vouch for a fact: I can vouch for the quality. Note voucher, which is the same word: a document that vouches for value; and that vouchsafe, meaning to grant something condescendingly, is the same vouch plus safe and is now entirely archaic.
1verbvouchTo state that you can answer for somebody's honesty.
“I've known her for years, and I can vouch for her honesty.”
vouch is a guaranteeing.
Old French vochier means to call or summon, from Latin vocare — the same verb as voice, vocation and invoke. Vouching for somebody is calling on your own name as a witness.
Proto-Indo-European
*wekʷ- — to sound out; to speak
Latin
voco — to call, summon; to call upon, invoke; to designate, name; to bring or put (into a condition or state
Vulgar Latin
*vocico
Old French
vochier — to call, summon; to claim; to call upon, invoke; to denounce
Anglo-Norman
vochier
Middle English
vouchen — to call, summon; to provide; to make available, proffer; to affirm, declare formally
English, today
vouch
The verb is derived from Middle English vouchen (“to call, summon; to provide; to make available, proffer; to affirm, declare formally”)fouche, voche, vouch, vouche, voutsche, vowch, woch, wouche, wowche, (Northern England) veuche, (Scotland) woche, from Anglo-Norman vochier, and Old French vochier (“to call, summon; to claim; to call upon, invoke; to denounce”)voker, vouchier, vougier, voukier, from Vulgar Latin vocico, derived from Latin voco (“to call, summon; to call upon, invoke; to designate, name; to bring or put (into a condition or state”), ultimately from Proto-Indo-European wekʷ- (“to sound out; to speak”). Verb sense 8.1 (“to summon (someone) into court to establish a warranty of title to land”) in the form vouch to warrant or vouch to warranty is a Anglo-Norman - and Old French voucher a garant. The noun is derived from the verb.
Etymology from Wiktionary, CC BY-SA