The compound adjective 'well-kept' is a transparent combination of two native English elements. The adverb 'well,' with roots in Proto-Germanic wel and ultimately Proto-Indo-European welh₁- (to wish, will), conveys the notion of goodness or satisfactoriness. The participle 'kept' originates from the Old English verb cēpan, meaning to hold or observe, which evolved from a West Germanic base related to catching or seizing. The literal logic of "held well" or "maintained in a good manner" directly underlies both primary definitions, whether describing the physical care of property or the figurative holding of a secret securely.

Structure: well (in a good manner) + kept (past participle of 'keep') - well: From Old English wel, meaning "in a good manner, satisfactorily." It functions as an adverb modifying the participle. - kept: From Old English cēpan (to seize, hold), its past participle form. It functions as the core verbal element meaning "maintained" or "held."