to bear witness to; certify; declare to be correct, true, or genuine; declare the truth of, in words or writing, especially affirm in an official capacity: to attest the truth of a statement.
2.
to give proof or evidence of; manifest: His works attest his industry.
3.
to put on oath.
verb (used without object)
4.
to testify or bear witness (often followed by to ): to attest to the reliability of an employee.
1540s, from M.Fr. attester, from O.Fr. atester (13c.) "affirm, attest," from L. attestari "confirm," lit. "bear witness to," from ad- "to" + testari "bear witness," from testis "witness" (see testament).