This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鞕 combines 革 (leather) with 更, but the exact historical development is uncertain. It may have originally expressed something related to leather or hardness, but the modern form is rare and its origin is not well documented.
The kanji has 革 (leather) on the left and 更 (renew) on the right. Since its meaning is uncertain, picture stiff leather being renewed to make it hard and firm, matching the kun-reading かた.い (hard).
For ゴウ, imagine a leatherworker named Go who hardens leather: Go -> ゴウ, and his work makes the leather かた.い.