'lavishly-designed' is a compound of 'lavishly' and 'designed'. 'lavish' originates from Middle English, ultimately of Old French influence (early forms include 'lavish'/'laviche'), where the root carried the sense of 'abundant' or 'excessive'. 'designed' comes from Latin, specifically the word 'designare', where 'de-' meant 'completely/away' and 'signare' meant 'to mark or sign'.

'lavish' evolved from Middle English forms and Old French influences into the modern English adjective 'lavish', which led to the adverb 'lavishly'. 'designare' passed into Old French as 'designer' and then into Middle English as 'design', later developing verb and noun senses and the past participle 'designed'.

Initially, 'lavish' carried the idea of abundance or excess; over time it shifted to emphasize generosity or extravagance (often ornamental). 'designare' originally meant 'to mark out' or 'to designate'; it evolved into the modern senses of 'to plan' or 'to create a plan or appearance', which informs 'designed'. Together, the compound means 'planned or created in an extravagant/ornate way.'