The word 'topical' originates from the Greek topos, meaning 'place' or 'commonplace', which entered Latin as topica referring to general themes or commonplaces of argument. In rhetoric, a 'topic' was a general line of argument applicable to many situations, a conceptual 'place' one could go to find material. Over time, 'topic' narrowed to mean the subject of discussion. The adjective-forming suffix '-al' was added, creating 'topical' to describe something pertaining to a current subject or theme. The modern sense of 'locally applicable' or 'current' retains the original Greek idea of relating to a specific 'place' in discourse or time, while the medical use ('applied to a body part') directly echoes the ancient sense of a physical location.

Structure: topic (subject) + al (adjective suffix) - topic: From Latin topicus, from Greek topikos ('of a place'), from topos ('place'). In this word, it functions as the core root meaning 'subject' or 'matter'. - al: A suffix of Latin origin (-alis) used to form adjectives meaning 'of, relating to, or characterized by'.