Dan. spenna n. “white fog”
A noun glossed “white fog” developed from the root ᴹ√SPAN (Ety/SPAN, EtyAC/SPAN), perhaps from a primitive form *✶spannā as suggested by Helge Fauskanger (AL-Nandorin/spenna). As noted by Helge Fauskanger, it seems the primitive vowel [a] became [e]. The mechanism is unclear, but perhaps this change was triggered by the initial [s] plus voiceless stop.
References ✧ Ety/SPAN; EtyAC/SPAN
|ᴹ√SPAN > spenna||[spannā] > [spennā] > [spenna]||✧ Ety/SPAN|