indorse

Etymology

An alteration of Middle English endosse under the influence of Medieval Latin indorsare. Endosse came from Old French endosser (“to put on back”), from Latin dossum, an alternative form of dorsum (“back”), the same root that gives dorsal (“of the back”). In other words, the ‘r’ was lost in Latin dossum, which passed into Old French and then Middle English as endosse; the ‘r’ was later restored in English through Medieval Latin indorsare, which had kept it, and at the same time the French ‘e’ was swapped for the Latin ‘i’ (in-, rather than en-). The alternative spelling endorse, now more common, keeps the restored ‘r’ but goes back to the initial ‘e’ rather than the Latinate ‘i’.