There was a word rochben “rider” (of any gender) in the Quendi and Eldar essay of 1959-60, a combination of roch “horse” with the suffix -ben “person” (WJ/376). Tolkien used it as an example of how Sindarin plurals applied only to the second element of recognized compounds: pl. rochbin “riders” rather than **rechbin; compare more ancient roechbin [rœchbin] where the plural mutation applied to the entire word, and modern erphin “nobles” plural of arphen [< *ar-pen], which is no longer recognized as a compound.

In notes on The Ride of Eorl, Tolkien instead had rochon “rider” in the song-name Rochon Methestel “Rider of the Last Hope” (UT/313). Since this used the masculine suffix -on, this was presumably a specifically male rider, as opposed to a female rider which might be *rochil.