'larvae-harboring' is a compound built from English 'larvae' + 'harboring'. 'larvae' comes from Latin 'larva', where 'larva' originally meant 'ghost' or 'mask' and was later adopted in scientific Latin to denote the immature form of an insect. 'harbor' comes from Old English elements (see below) meaning 'shelter' or 'refuge'.

The Latin 'larva' passed into New Latin/early modern scientific use to mean the immature stage of arthropods, giving English 'larva' (plural 'larvae'). 'Harbor' descended from Old English elements (e.g. 'herebeorg'/'herberga' meaning 'army-shelter' or 'shelter'), through Middle English (e.g. 'herberge', 'harbergh') to modern English 'harbor'. The compound formation ('larvae' + present participle of 'harbor') follows modern English compounding patterns to create an adjectival phrase meaning 'providing shelter for larvae'.

Originally Latin 'larva' meant 'ghost/mask', but its meaning shifted in scientific contexts to 'immature insect stage'; 'harbor' originally meant a shelter or place of refuge and has retained this core sense. The compound's meaning came to be 'containing or providing habitat for larvae'.