Children are naturally curious and easily learn words. If the adults in your life knew what an organism was called and told you the name as a child, you probably remember it. If they didn’t know, then you don’t know. Unfortunately this means knowledge goes down over time, especially if people move to a new area and then don’t speak the language or simply don’t recognize the species there. They may recycle names they do know, incorrectly applying them to different species. I grew up calling Cotinis mutabilis “Japanese Beetle,” probably because my grandparents came from the east coast and had probably seen Popillia japonica there, so any green shiny beetle was close enough.
Last week my mom told me her father (of German decent) called bees (or wasps?) that live in the ground “schnickelfritz.” Google tells me it’s a Pennsylvania Dutch term of endearment for a mischievous child, meaning something like “little rascal.” No mention of insects though!