'inconsistently-employed' is a compound formed from 'inconsistently' + 'employed'. 'inconsistently' comes from the negative prefix 'in-' + 'consistent' + the adverbial suffix '-ly'; 'consistent' ultimately derives from Latin 'consistere' meaning 'to stand together'. 'employed' is the past participle of 'employ', which entered English from Old French 'employer' (modern French 'employer').

'in-' + 'consistent' developed into English 'inconsistent' and then 'inconsistently' by adding '-ly'. 'employ' came into Middle English as 'employen' from Old French 'employer' and developed the past participle form 'employed', which combined with adverbs (e.g. 'inconsistently') to form phrases like 'inconsistently employed'.

Originally, roots like Latin 'consistere' conveyed ideas of 'standing together' or 'stability', and over time 'consistent' came to mean 'regular' or 'steady'. 'Employ' originally meant 'to use or apply' and later specifically 'to hire or provide work'; together, the compound came to mean 'hired or working in an unstable/irregular way'.