1350-1400; variant (with en- for in-) of earlier indorse < Medieval Latinindorsāre to endorse, equivalent to Latinin-in-2 + -dorsāre, derivative of dorsum back; replacing endoss,Middle Englishendossen < Old Frenchendosser, equivalent to en-en-1 + -dosser, derivative of dos < Latindorsum
endorser, endorsor, noun
preendorse, verb (used with object), preendorsed, preendorsing.
reendorse, verb (used with object), reendorsed, reendorsing.
subendorse, verb (used with object), subendorsed, subendorsing.
superendorse, verb (used with object), superendorsed, superendorsing.
late 14c., from O.Fr. endosser, lit. "to put on back," from en- "put on" + dos "back," from L. dossum, var. of dorsum. Sense of "confirm, approve" (by signing on the back) is first recorded in Eng. 1847. Assimilated in form to M.L. 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]