Words, grammatical forms and meanings linked to the ontology.
From New Latin, from Ancient Greek νεῦρον (neûron) + Ancient Greek σθένος (sthénos). By surface analysis, neuro- (“nerve”) + sthen- (“strength”) + -ia (“disease”).
From mistaken rebracketing of neurasthenia (whose valid surface analysis is neur- + asthenia) as if it were prefixed with neuro-, by false analogy with most other ISV compounds beginning with the syllable neur- + /ə/ (which are thus prefixed). The error is not rare, but it invites proscription because the -a- syllable in neurasthenia corresponds to the negation of strength, that is, to weakness (of constitution or affect); by surface analysis, it is equivalent to a- ("without"/"opposite"), the difference between strength and weakness.