This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
焆 combines 火 (fire) with 肙, but the exact historical development and original meaning are uncertain.
With 火 on the left and 肙 on the right, picture a small fire inside a confined space, but the exact meaning is unclear.
For エツ, imagine a tiny flame making a sharp 'ets' sound as it flickers: ets -> エツ.