Probably a dialectal variant of Middle Low German ēkel (“disgusting”), from which German Ekel (“loathing, disgust, fastidiousness”). A connection to Proto-Germanic *aikulaz (“fearful”) has been suggested for both words; compare Old English acol (“burdensome, troublesome”), English ache, Galician extern (“to vex”), Dutch akelig (“terrible”).
Heikel seems to have arisen out of 16th century Upper German dialects with a first meaning “easily disgusted, choosy”. Dialectal variants include Bavarian haglich and hoaglich (both akin to regional German heikelig or heiklig), Swabian haikel, Alemannic German heikχel, Saterland Frisian hekel (“fastidious with regard to food”).
Others have suggested a derivation from Middle High German heien, heigen (“to cherish, harbour”) (compare Bavarian haigeln). The connection with the root of English irk (“to irritate, annoy, bother”), advanced by the Grimms, seems to be out of question today, even given the Upper German verb erkeln (“to loathe”).
heikel (strong nominative masculine singular heikler or (extremely rare) heikeler, comparative heikler or (extremely rare) heikeler, superlative am heikelsten)
1Extremely rare.
1Extremely rare.