can’t believe I only just learned about the attested Gaulish word “marcosior” (< PCeltic *marko- ‘horse’ but as a passive verb in the desiderative or future) which means “I want to be ridden like a horse” and occurs in exactly the context you’re imagining
that was fast. easy website
im seeing people fact-check this in the notes so i'll add that the full inscription is "marcosior maternia" and if you search that in google scholar you'll find lots of sources. it might not be true but it's definitely real, by which i mean that scholars don't know for sure what "marcosior maternia" means but this is a common interpretation. it's written on a spindle whorl (little weights that are used in spinning) and there's actually a lot of spindle whorls from roman gaul that have sort of amatory inscriptions on them, so they might have been gifts for lovers but it's not clear, but anyway a sexual meaning is perfectly expected for this type of object, and maternia looks like a woman's name in either the nominative or instrumental case, and marcosior looks like a passive verb related to the word for 'horse' in a desiderative or future form. so "i want to be ridden by maternia", "i will be ridden by maternia", and "maternia will be ridden" are some of the plausible interpretations.
also i didnt emphasize in the post just how fragmentary this language is. there's only a few hundred inscriptions in gaulish and theyre short. we dont know if there was an optative mood. but we do know how to say something about getting ridden by maternia
