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.

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Definitions of cub from WordNet
cub (n.)
an awkward and inexperienced youth;
Synonyms: greenhorn / rookie
cub (n.)
a male child (a familiar term of address to a boy);
Synonyms: lad / laddie / sonny / sonny boy
cub (n.)
the young of certain carnivorous mammals such as the bear or wolf or lion;
Synonyms: young carnivore
cub (v.)
give birth to cubs;
bears cub every year