tickle, funny
擽 centers on the sensation and reaction of tickling: a light touch that provokes laughter or a funny, tingling feeling.
擽 combines 扌 (hand) with 樂, which likely contributes the sound and may relate to the idea of pleasure or music, suggesting a hand action that causes a ticklish, pleasurable sensation.
A hand 扌 beside 樂 (music/pleasure) suggests fingers dancing lightly to create a ticklish, funny feeling.
For リャク, imagine a tickle so sudden it makes you yelp 'ryak!' — the sharp sound リャク matches the surprise of being tickled.
tickling; tickle