Bookworm is a native compound, made the old Germanic way: take two ordinary words and push them together. Both halves are Old English, and the result needs no explanation to anyone who knows them — which is precisely the point. Where Latin and Greek build long words out of prefixes and roots most speakers cannot parse, English's native habit is to glue plain words end to end: handbook, sheepdog, bookworm, ring-giver.
The metaphorical sense came first, oddly enough. From the 1540s a bookworm was a person devoted to study; only by the 1650s was the term turned on the actual larvae that chew holes through old bindings and pages. There is no single insect properly called a bookworm — the name gets applied to anobium beetle larvae, silverfish and booklice indifferently, which suggests people were more interested in the insult than in the entomology.
bookworm (n.) 1540s, "person devoted to study;" by 1650s in reference to the larvae of certain insects that eat holes in the bindings and paper of old books; see book (n.) + worm (n.). There is no single species known by this name, which is applied to the larvae of the anobium beetle (woodworm), silverfish, and booklice. also from 1540s
bookworm came in through Old English, and its spelling follows that family's conventions.
What gives it away on the page
| compounds instead of borrowings | The native strategy for new words: glue two old ones together.handbook, sheepdog, bookworm |
Old English in the spelling guide · guess another word's family