The word "subhead" is a modern English compound formed by directly combining the Latin prefix "sub-" with the native English word "head." The prefix "sub-," deriving from the Latin preposition meaning "under, below, or close to," was adopted into English to indicate a lower rank or secondary position. The element "head" evolved from the Old English hēafod, which, beyond its primary meaning of the body part, developed the metaphorical sense of the top or foremost part of something, including a title. Therefore, a "subhead" logically denotes a secondary or subordinate heading positioned beneath a main head, illustrating a clear, compositional formation from its constituent parts.

Structure: sub (under) + head (heading) - sub: A prefix of Latin origin, meaning "under," "below," or "secondary." - head: A word of Old English origin (from hēafod), here used in the sense of a title or heading at the top of a section.