What does 고사리 같은 손 mean?

ANSWER: a fern-like hand

A couple of days ago, I began reading a Korean book entitled "뜻도 모르고 자주 쓰는 우리말 숙어 1000 가지," which translates as "1000 Korean Idioms We Frequently Use Without Knowing Their Meanings." Below, I have translated the description for Idiom #48:

A Fern-like Hand (고사리 같은 손)

In the early spring (이른 봄), in the sunny spots of mountains and fields (산과 들의 양지바른 곳에는), one can see plump-looking things sprouting with young stems that are coiled at their ends (통통하게 생기고 끝이 말린 어린줄기가 움트는 것을 볼 수 있다). As they grow (그것이 자라면서), the coiled stems (말렸던 줄기가) uncoil (펴지고), and to their left and right (좌우로는) other stems extend with many leaves suspended (많은 잎들을 매단 또 다른 가지가 뻗는다). These [plants] are [fiddlehead] fern (이것이 고사리이다). LINK

As for the young fern (어린 고사리는), we gather and eat them as wild greens (캐어서 나물를 해 먹는데), and they are representative of the indispensable wild greens [used] at religious ceremonies (제사에 빼놓을 수 없는 대표적인 나물 중 하나이다).

When we say “고사리 같은 손” (고사리 같은 손이라고 할 때), the image to keep in mind is the coiled stems of the young fern (고사리는 그 말려 있는 상태의 어린 고사리를 염두에 둔 것이다). They look just like a child's hand clinched in a fist or a slightly opened fist (주먹을 쥐거나 약간 주먹을 벌린 듯한 모양이 마치 아이의 손과 같다), which is how the expression came into being (하여 생긴 표현이다).

EXAMPLE SENTENCE  

The children who finished their New Year's greetings (세배를 마친 아이들은) stuck out their fern-like hands (고사리 같은 손을 내밀어) and received the New Year's gift money grandfather gives out (할아버지가 주는 세뱃돈을 받았다).  

고사리

 Photo by Rror - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4072985

Link to a Preview of the Korean Book