Without a cob, or lacking the central woody core of corn or a male swan.
From English 'cob' (the hard center of an ear of corn, or a male swan) plus the suffix -less meaning 'without or lacking.'
Corn cobs have become surprisingly useful—farmers now use them for biofuel, animal bedding, and industrial abrasives, so 'cobless' corn is actually less valuable now than it used to be!
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