A variant or related form referring to the head or head-like structure in zoology, though it's a rare or archaic usage.
From Greek kephalē (head) + the neuter suffix -om/-on. This appears to be an older or specialized anatomical term that combined the standard Greek root with classical suffix patterns.
Many scientific terms have 'dead' variants that scientists stopped using—like how we say 'cephalopod' instead of 'cephalom' now because one stuck and the other faded from fashion.
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