the compound adjective 'well-balanced' is a relatively modern english formation, emerging in the 18th century. it combines the old english adverb 'well', signifying a satisfactory or good condition, with the verb 'balance', derived from the latin 'bilanx' (having two scales). the literal sense of 'evenly poised' was first applied to physical objects. the semantic logic extends from this physical equilibrium to abstract concepts: a 'well-balanced' diet contains varied elements in proper proportion, and a 'well-balanced' mind possesses emotional stability and sound judgment, metaphorically maintaining an even keel.

Structure: well (to a good standard) + balance (equilibrium) + ed (adjective suffix) well (old english, adverb used as an intensifier/qualifier); balance (latin via old french, noun/verb root meaning equilibrium); ed (old english, suffix forming adjectives from verbs or nouns).