The term "transsexual" is a modern compound, formed in the mid-20th century by combining the Latin prefix 'trans-' with the adjective 'sexual'. The prefix 'trans-', meaning "across" or "on the other side of," is used metaphorically to signify a crossing from one state to another, in this case, a crossing of sexes or genders. The base 'sexual' anchors the term in the concept of biological sex and gender identity. Thus, the word's literal construction, "across sexual," logically evolved to describe the experience of a person whose gender identity is opposite to their sex assigned at birth, emphasizing a transition or crossing between these states.

Structure: trans (across) + sexual (relating to sex) - trans: Latin origin, from 'trans-' meaning "across, beyond, through." Acts as a prefix indicating change or crossing over. - sexual: Latin origin, from 'sexus' meaning "state of being male or female." Acts as the base word, forming an adjective relating to biological sex or gender.