Is it farther or further?
mid-14c., "to declare the truth of," also "to vouch for or confirm" (an official record, etc.), from Old French certefiier "make certain, witness the truth of" (12c.), from Late Latin certificare "to certify, to make certain," from Latin certus (see certain) + root of facere "to make, do" (see factitious). Also used in Middle English in broader senses of "inform, give notice; instruct, to direct; to designate." Related: Certified; certifying. Certified public accountant attested from 1896.