The word 'undernourished' is a modern English compound formed from the prefix 'under-' and the past participle of the verb 'nourish'. The prefix 'under-', of Germanic origin, carries the sense of insufficiency or deficiency. The core verb 'nourish' traces back to the Latin 'nutrire', meaning "to suckle, feed, or foster," which itself is derived from the Proto-Indo-European root sna-/snu- ("to flow, to drip"), a root also related to nutrition and nurture. The suffix '-ed' transforms the verbal concept into an adjectival state. Thus, the literal logic of the morphemes—"being in a state of being fed below what is necessary"—directly and transparently conveys the modern abstract meaning of suffering from a lack of adequate food for health.

Structure: under (below) + nourish (feed) + ed (adjective suffix) - under: Old English; a prefix meaning "beneath, below, less than." - nourish: Old French (nourrir), from Latin (nutrire); a verb root meaning "to feed, to sustain." - ed: Old English; a suffix used to form adjectives from verbs, indicating a state or condition.