驚く
おどろく · odoroku · JLPT N4 · verb-godan
to be surprised
🐴 驚 = respect (敬) + horse (馬): a horse so startled it stiffens
The kanji stacks 敬 (respect, here also giving the sound) over 馬 (horse) — the original sense was a horse shying in fright. Sound hook: odoROKu has a ROCK in it — a rock drops, oh-doh!, and you are astonished.