will o' the wisp

• will-o'-the-wisp, will-o'-wisp

Will (“male given name”) + of + the + wisp (“bundle of straw or hay used as a torch”)[1]

• (US) IPA^(key): /ˌwɪləðəˈwɪsp/

will o' the wisp (plural will o' the wisps)

1. (British folklore) A strange light that attracts travellers from pathways into dangerous marshes or graveyards.
2. (idiomatic) A delusionary or otherwise unachievable goal that one feels compelled to pursue.
   • 1992 March 2, Richard Preston, The New Yorker, "The Mountains of Pi":

     I happen to think the brothers’ pi project is a will-o’-the-wisp, and is one of the least interesting things they’ve ever done. But what do I know?

• (strange light): ignis fatuus, spooklights, ghost lights, nightfire; hinkypunk (west Country dialect); jack o'lantern (US)

• Min Min lights

• "Will o’ the wisp" at Folklore of the British Isles