This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
胍 combines the flesh component ⺼ with 瓜 (melon/gourd). The exact historical development is uncertain, but it likely originally referred to a part of the body or a type of swelling, possibly related to the shape of a gourd.
The left side ⺼ suggests flesh or body, and the right side 瓜 looks like a melon on a vine. Picture a strange bodily growth shaped like a gourd, but remember that its actual meaning is unclear.
For コ, imagine a small gourd-shaped lump on the body that makes you say 'co' in surprise: co -> コ.