Endorser

[en-dawrs] /ɛnˈdɔrs/

verb (used with object), endorsed, endorsing. Also, (for defs 1–6).
1.
to approve, support, or sustain:
to endorse a political candidate.
2.
to designate oneself as payee of (a check) by signing, usually on the reverse side of the instrument.
3.
to sign one’s name on (a commercial document or other instrument).
4.
to make over (a stated amount) to another as payee by one’s .
5.
to write (something) on the back of a document, paper, etc.:
to endorse instructions; to endorse one’s signature.
6.
to acknowledge (payment) by placing one’s signature on a bill, draft, etc.
noun
7.
Heraldry. a narrow pale, about one quarter the usual width and usually repeated several times.
/ɪnˈdɔːs/
verb (transitive)
1.
to give approval or sanction to
2.
to sign (one’s name) on the back of (a cheque, etc) to specify oneself as payee
3.
(commerce)

4.
to write (a qualifying comment, recommendation, etc) on the back of a document
5.
to sign (a document), as when confirming receipt of payment
6.
(mainly Brit) to record (a conviction) on (a driving licence)
v.

late 14c. endosse “alteration,” from Old French endosser (12c.), literally “to put on back,” from en- “put on” (see en- (1)) + dos “back,” from Latin dossum, variant of dorsum.

Sense of “confirm, approve” (by signing on the back) is recorded in English first in 1847. Assimilated 16c. in form to Medieval Latin indorsare. 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]