squab n.

1680s, "very young bird," earlier (1630s) "unformed, lumpish person" and used at various times for any sort of flabby mass, such as sofa cushions; probably from a Scandinavian word (compare dialectal Swedish skvabb "loose or fat flesh," skvabba "fat woman"), from Proto-Germanic *(s)kwab-. Klein lists cognates in Old Prussian gawabo "toad," Old Church Slavonic zaba "frog."