scratch, crawl
爬 centers on movement using claws or limbs close to a surface: scratching with nails and crawling along the ground.
爬 combines 爪 (claw) with 巴, which likely contributes the sound. The claw suggests scratching or crawling with claws.
The claw 爪 wraps around 巴 like a creature using its claws to scratch or crawl. Picture a crab's claw gripping the ground as it scratches and crawls.
For ハ, imagine a claw scratching a hard surface with a sharp 'ha!' sound: ha -> ハ, and the claw leaves scratch marks.