'larval-growth-promoting' originates from modern English compounding of the adjective 'larval', the noun 'growth', and the verb 'promote'. 'larval' ultimately comes from Latin 'larva' (meaning 'mask; ghost', later used in biology for immature insect forms), 'growth' from Old English roots related to 'grow', and 'promote' from Latin 'promovere'.

'larval' developed via New Latin from Latin 'larva' and came into English scientific usage as 'larval' meaning 'of or relating to a larva'; 'growth' evolved from Old English 'growan'/'grōwan' into the modern noun 'growth'; 'promote' came from Latin 'promovere' (pro- 'forward' + movere 'to move') and entered English via Old French/Latin influence, producing the modern verb 'promote', which combines with nouns to form compound modifiers like 'growth-promoting'. These elements were later compounded as descriptive hyphenated phrases such as 'larval-growth-promoting'.

Initially the component words carried their original senses (e.g. Latin 'larva' for an apparition or mask, Old English roots for 'grow', Latin 'promovere' for 'move forward'), but in scientific/biological contexts they evolved into the specific combined meaning 'causing or favoring the growth of larvae', which is the modern sense of the compound.