freeze, be cold, be clear, attain skill
冱 centers on a state of cold stillness: freezing, being cold, or becoming clear and sharp like ice. The sense of attaining skill is a rare extension, possibly from the idea of a clear, settled mind.
冱 combines the ice radical 冫 with 互, which likely contributes a phonetic element. The character is associated with freezing and cold, but the exact historical development is uncertain.
The ice radical 冫 on the left shows cold, and the right side 互 looks like a frozen, interlocking pattern. Picture ice crystals locking together in a clear, still freeze.
For ゴ, imagine a frozen lake so clear you can see a go board (碁, ご) trapped under the ice: go -> ゴ, and the cold preserves it perfectly.