Genealogies of the two known members of the Chubb family, Adamanta (who married into the Tooks) and Chica (who married into the Baggins family). The relationship between the two is not known, but Adamanta's youngest child Isengar was born at about the same time as Chica. This probably places Adamanta in the same generation as Chica's unnamed mother (and indeed the two may have been sisters, which would make AdamantaChica's aunt).
Tolkien explains the origins of the name Chubb in his notes for translators, associating it with the adjective 'chubby' (meaning 'plump' or 'rounded'). That word is in turn said to derive from the river fish known as the chub, which has a somewhat rounded shape. How the fish originally came by this name is not known.