This Proto-Japonic entry contains original research. The reconstruction in this entry is based on published research, but the specific form presented here is not found in prior works.
A surface analysis suggests a derivation from *ataru, however the only phonetic match is 当たる(ataru, “to get hit, to compete”, attested 720). A standalone adverb in Old Japanese 可惜(atara, “regrettably”) exists, so it might be derived from the adverb.