also: ひょっくり
adverb, adverb taking the 'to' particle
suddenly; unexpectedly; by chance
Mimetic adverb describing something appearing or happening abruptly, often with a sense of surprise or casualness. Commonly used with と (ひょっこりと).
彼がひょっこりと部屋に入ってきた。
He suddenly came into the room.
ひょっこり昔の友達に会った。
I unexpectedly ran into an old friend.
ふと is used for actions done unintentionally or on a whim, whereas ひょっこり emphasizes the suddenness of an appearance or occurrence.
Mimetic word; the exact origin is uncertain, but it likely derives from the sound-symbolic element ひょっ, suggesting a light, sudden movement or appearance.