Cub

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mid 16th century: of unknown origin.

wiktionary

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From earlier cubbe. Origin unknown. Compare Old Norse or Icelandic kobbi(“seal”), Old Irish cuib(“whelp”). [1] Compare also English cob.

cub (plural cubs)

etymonline

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cub (n.)

1520s, cubbe "young fox," of unknown origin, not recorded in Middle English; perhaps from Old Irish cuib "whelp," or from Old Norse kobbi "seal." Extended to the young of bears, lions, etc., after 1590s. The native word was whelp. Cub Scout is from 1922.