をして

Etymology
Derived as a combination of accusative / object particle + the conjunctive form  of classical verb, modern verb. Used to mark the indirect object or patient of a causative expression. This appears very early in the written record in the , completed in 797 CE, representing late- and early- Japanese. This usage persists in the modern language, but is restricted to formal literary writing.

Usage notes
Historically used primarily in the Japanese reading of. Later, in works written natively in Japanese, the was omitted and just  was used instead. Over time, with the  again became common, and in the modern language, this is used exclusively in literary contexts to impart a traditional and formal tone.

Prior to the mid-, the verb was not necessarily conjugated in the causative, and was used to mark the subject of the action. Starting from the mid-, the verb was conjugated with the causative auxiliary in the classical form or  in the modern form.

In modern non-literary Japanese, this has been superseded by the particle for intransitive verbs (, jidōshi), and  for transitive verbs (, tadōshi), together with the standard causative endings  or.