'nonmyelinated' originates from English, specifically the prefix 'non-' plus the word 'myelinated', where 'non-' meant 'not' and 'myelinated' meant 'having a myelin sheath.'

'nonmyelinated' changed from the combination of 'non-' + 'myelinated'. 'Myelinated' derives from the verb 'myelinate' (formed in modern English from the noun 'myelin' plus the verb-forming suffix '-ate'), and 'myelin' came into scientific use from Neo-Latin/Modern German 'myelin' ultimately from Greek 'myelos' meaning 'marrow'.

Initially, the Greek root meant 'marrow'; over time it came to denote the fatty substance forming nerve sheaths ('myelin'), then 'myelinated' meant 'having a myelin sheath', and 'nonmyelinated' developed to mean 'lacking that sheath.'