The English term will-o’-the-wisp means, to quote the definition in Wordsmyth, ‘a phosphorescent light that appears to hover over marshes at night, possibly arising from spontaneous combustion of marsh gases.’ The phrase used to be will of the wisp, and before that will with the wisp. Wordsmyth defines wisp as ‘a thin bundle, bunch, tuft, streak, or the like, as of straw, hair, or smoke,’ which makes sense as a description of the hazy atmospheric occurrence. But what about will? There’s no reason to think it’s the will that expresses volition or futurity, but let’s suspend judgment on that for the time being. (And speaking of judgment, mine is that in America we ought to spell the word the way the British do: judgement, with the e that indicates a “soft” g.)
The first part of will-o’-the-wisp turns out to be the name Will, apparently chosen as a personification of the mysterious phenomenon in the same sort of way that Jack got chosen for jack-o’-lantern, but with the bonus of the alliteration in will with the wisp (in fact that may have been too much alliteration, as the change to will of the wisp implies).
The male name Will is short for William, from French Guillaume, and finally we see a connection to Spanish, which renders the name Guillermo. The Spanish and French forms go back to Medieval Latin Guillelmus or Gilgelmus, but they had come from Old High German Willahelm. Historical German names usually consisted of two elements, and that was the case here. The first part was wil, meaning ‘will, desire,’ so indirectly that is the will in will-o’-the-wisp. Latin velle ‘to want’ was a native cognate, and from that root we have volición/volition.
The second part of the Germanic compound was helm, meaning ‘helmet’ or more generally ‘protection.’ Germanic helm led to Old French helme, whose diminutive has become English helmet. The Germanic word similarly entered into Spanish, which has retained it as yelmo.
© 2016 Steven Schwartzman