the word 'unhealthful' is a modern english formation built upon the old english root 'health,' which itself derives from the proto-germanic 'hailithō,' meaning "wholeness." the negative prefix 'un,' also of germanic lineage, is attached to negate the core concept. the adjectival suffix '-ful,' from old english '-full,' transforms the noun into an adjective meaning "characterized by" the absence of health. thus, the literal construction "not full of health" logically evolved to describe conditions or substances detrimental to physical well-being.

Structure: un (not) + health (state of well-being) + ful (full of) un: a prefix of germanic origin, meaning "not," used to give a negative force. health: a noun of old english origin (hǣlþ), meaning "wholeness, a being whole." ful: a suffix of old english origin (-full), meaning "full of" or "characterized by."