'third-party' originates from the combination of 'third' and 'party,' where 'third' refers to the number three and 'party' refers to a group or individual involved in a situation.

The term 'third-party' evolved from legal and business contexts where a third entity is involved in a transaction or agreement.

Initially, it referred to any third entity involved in a legal or business context, and this meaning has largely remained the same in modern usage.