'non-cachectic' is formed from the prefix 'non-' (from Latin, used in English to mean 'not') combined with 'cachectic', which comes from medical New Latin 'cachecticus' ultimately from Greek 'kakhexis' (κακῆξις).

'cachectic' entered English via New Latin/Modern medical usage from Greek 'kakhexis' (κακῆξις) meaning a 'bad condition' or 'wasting state'; the adjective form 'cachectic' (or 'cachecticus' in Latin) became established in medical English in the 19th century, and 'non-' was later prefixed in English to create 'non-cachectic'.

Originally tied to the general idea of a 'bad condition' or wasting state in Greek/Latin, it evolved into the specific clinical meaning 'affected by cachexia (severe wasting)' — 'non-cachectic' therefore denotes the absence of that clinical wasting.