The Spanish verb 'mediar' (meaning 'to mediate') comes from the Latin verb 'mediare', which meant 'to be in the middle'. This Latin verb was itself derived from the Latin adjective 'medius' meaning 'middle'. The evolution from the concept of being in the middle to mediation makes intuitive sense, as a mediator typically positions themselves between two parties to help resolve conflicts or facilitate agreements.

Several common Spanish words share this same Latin root 'medius', including: 'medio' (middle, half), 'mediodía' (noon, literally 'middle of the day'), and 'mediante' (by means of, through). All these words retain some connection to the original concept of being in the middle or between things.

English speakers can recognize this same Latin root in many familiar words such as 'medium' (middle size/quality), 'median' (middle value), 'immediate' (with no middle/intervening time), and of course 'mediate' itself. The word 'intermediate' also comes from this root, literally meaning 'between middles' or 'in the middle of'.