gloaming

From a dialectal variant of glooming, from Middle English *gloming, from Old English glōmung, from Old English glōm (“twilight”). By surface analysis, gloom + -ing. Related to glow. The OED notes: "The vowel of the modern gloaming is anomalous, as Old English glōmung should normally become glooming. The explanation is probably that the ō was shortened in the compound ǣfen-glommung (as the spelling seems to show was actually the case), and that from this compound there was evolved a new subject glŏmung, which by normal phonetic development became Middle English glǭming, modern English gloaming."