Derivational etymology implying one formal manipulation, the lengthening of the initial [o]. The donkey was an affordable animal, contrary to the horse. However, it is likely that this etymology results from a misunderstanding of the older etymology by ὀνίνημι given by Orion (see ὄνος / ὀνίνημι): in Late Greek, the quantity distinction between ο and ω was lost, so that ὄνησις "utility, profit" could be confused with ὤνησις "buying". This would explain why the older etymology is missing in the Excerpta and replaced by this one.