c. 1600, "linger in expectation;" 1640s, "have a longing or craving for," of unknown origin. Probably from Flemish hankeren, related to Dutch hunkeren "to hanker, to long for," which is perhaps an intensive or frequentative of Middle Dutch hangen "to hang" (see hang (v.)). If so, the notion is of "lingering about" with longing or craving. Compare English hang (v.) in hang on (someone's) every word. Related: Hankered; hankering.
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Harper, D. (n.d.). Etymology of hankering. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/hankering