The compound adjective "then-new" is a relatively modern English formation, combining two native Germanic words of ancient lineage. "Then" originates from Proto-Germanic þana, a demonstrative adverb of time, tracing back to the Proto-Indo-European demonstrative root to-. "New" stems from Proto-Germanic newjaz, from the PIE root newos-, meaning "new." The compound's logic is transparently descriptive, using "then" to anchor the quality of being "new" to a specific, referenced point in the past. It effectively captures the transient nature of novelty, indicating something that was innovative or freshly established at a prior moment but may no longer be so.

Structure: then (sense) + new (sense) - then: From Old English þonne, þænne, meaning "at that time, in that case." It functions as a temporal adverb specifying a particular past period. - new: From Old English nīwe, nēowe, meaning "recently made, fresh, novel." It functions as an adjective describing the state of being recent or unfamiliar.