According to Bulgarian Etymological Dictionary: * Either back-formed from the diminutive ръку́нка (rǎkúnka) of ръка́ (rǎká, “hand, arm”); * Or cognate with dial. Russian ку́на (kúna, “handful”), of unclear origin. Possibly from the root of dialectal Bulgarian ку́я (kúja, “to forge, to smith”).