down
氄 centers on soft, fine hair or down, like the fluffy under-feathers of birds or the delicate first growth of hair.
氄 combines 毛 (hair) with 矞, which likely contributes the sound and may relate to piercing or fine points, together suggesting fine, soft hair or down.
The right side 毛 means hair, and the left side 矞 looks like a complex tool or a bird's head with a crest. Imagine using a fine comb to gather the softest downy hair from a bird's crest.
For ジョク, imagine a soft down pillow that you joke about being too fluffy: joke -> ジョク, and the pillow is filled with fine down.