'spotlessly-constructed' is a Modern English compound formed from 'spotlessly' and 'constructed'. 'spotlessly' ultimately derives from Old English elements: 'spot' (Old English 'spot', a blemish) plus the suffix '-less' (Old English '-lēas', meaning 'without') and the adverbial '-ly'. 'constructed' comes from Latin 'construere', where 'con-' meant 'together' and 'struere' meant 'to pile up, build'.

'construct' changed from Latin 'construere' to Old French 'construire' and entered Middle English (e.g. forms like 'constructen'), becoming modern English 'construct' with the past participle 'constructed'. Separately, 'spot' (Old English 'spot') developed into Middle English 'spot' and combined with '-less' to form 'spotless' and later the adverb 'spotlessly'. These elements were later combined in Modern English into the compound adjective 'spotlessly-constructed'.

Originally, 'spotless' meant 'without spots (stains)' and 'construct' meant 'to pile up or build'. Over time, when combined as 'spotlessly-constructed', the phrase evolved to mean 'built without flaws or defects'—emphasizing precision and the absence of blemishes in construction.