An Etymological Dictionary of the German Language/Annotated/gewähren
gewähren, verb, ‘to be surety for, guarantee, attest,’ from Middle High German gewërn, Old High German giwërên, ‘to grant, confess, perform, pay, give security,’ also the equivalent Middle High German wern Old High German wërên; corresponding to Old Frisian wera, ‘to give security.’ From the Old High German participle wërênto, ‘guarantor,’ were adopted the Romance cognates, Italian guarento and French garant, ‘bondsman’ (allied to French garantir, Italian guarentire, ‘to give security,’ whence Modern High German Garantie, English warrant). The connecting link between the Old Teutonic weak verbal stem werai-, ‘to confess,’ and non-Teutonic words has not yet been found; perhaps Irish feraim, ‘I give,’ is allied.