'neatly-installed' is a compound of the adverb 'neatly' and the past participle 'installed'. 'neatly' originates from Old English, specifically the word 'nēt' (later Middle English 'net'/'neat'), where the root meant 'fit' or 'convenient'. 'install' originates from Latin, specifically the word 'installare', where 'in-' meant 'in' and 'stallare' (from 'stallum') meant 'place or set.'

'installed' changed from Medieval Latin/Old French forms into Middle English 'installen' and eventually became the modern English 'install' with past participle 'installed'. 'neatly' evolved from Old English 'nēt' through Middle English 'net/neat' to the modern adjective 'neat' and its adverbial form 'neatly'.

Initially, 'install' primarily meant 'to place or set in position' and 'neat' meant 'fitting' or 'convenient'; over time the components kept those placement and tidiness senses and combined into the compound 'neatly-installed', meaning 'placed or set up in a tidy manner.'