Where do we first see Cheshvan (as opposed to Marcheshvan)?

Question

The correct name for the eighth month of the Hebrew calendar is Marcheshvan. (See here and here.) This is how the name of the month appears throughout the Talmud (to the best of my knowledge) see e.g. Rosh Hashana 7a.

Colloquially, it is often shortened to just Cheshvan (to the extent that many think this is the correct name of the month).

Where is the first place we see the name written as Cheshvan?

Pri Chadash to Even HaEzer 126:7 writing in the latter half of the seventeenth century seems to assume that the "real" name is Cheshvan, so I imagine we would see sources before his time using the name Cheshvan for the month.

Answer 1

Midrash Abba Gurion to Ester (ed. Buber 3:7), which was redacted in the tenth century, refers to it as חשוון (Heshvan):

לתשרי זכות הרגלים, לחשוון זכות שרה

It is also found in Eisenbach's edition of the Rokeah's Sefer HaShem (page 133) from the late 12th-early 13th century:

ראש השנה א', חשון ב', כסליו א'

It is also found in Goldschmidt's edition of Sefer HaTerumot (56:1) from the early 13th century.

מכר מחשון וכתוב בו בחשון שנה שניה

The above editions of Buber, Eisenbach, and Goldschmidt respectively are all based on medieval manuscripts, so it seems clear that even if these are later corruptions, that it is at least medieval.

חשון is also found in Raavya (Pesahim 485), from the 12th century.