the word supplement originates from the latin 'supplementum', meaning 'that which fills up or completes'. this is derived from the verb 'supplere', which combines 'sub-' (under, from below) and 'plere' (to fill). the core concept is of adding something from below to fill a deficiency, thereby making something full or complete. this literal sense of 'filling up a lack' evolved into the modern abstract meanings of an addition that improves or completes something, or an extra section added to a publication.

Structure: sup (under, from below) + ple (fill) + ment (noun suffix) sup- (from latin 'sub-', meaning under, from below); -ple- (from latin 'plere', meaning to fill); -ment (from latin '-mentum', a suffix forming nouns denoting an action, result, or instrument).