You can picture an animal that has just been let out: it cannot hold still, it bounces off in one direction and then another, and the reason is that it feels good. Frisky is that , happy energy in a body. Both meanings of the word are the same energy; they differ only in where it is pointed.
可以想成一隻剛被放出來的動物：牠停不下來，一下衝這邊，一下彈那邊，而原因是牠心情好。frisky 畫的就是身體裡那股關不住的、開心的勁。這個字的兩個意思其實是同一股勁。差別只在那股勁往哪個方向去：一邊是跑跳玩鬧，一邊是想親熱。
From the word’s history
Frisky is frisk plus -y. Frisk itself carries the idea of skipping and leaping about, so the picture of a bouncing body is inside the word from the start.
frisky 是 frisk 加上 -y。frisk 本來就有「蹦蹦跳跳」的意思，所以「彈跳的身體」這個畫面從一開始就在字裡面。
Wiktionary etymology tree for frisky (frisk + -y), packet evidence source_ref kaikki:3f6f69a190036ae4:1018782613
登入就可以看每一支怎麼連回核心畫面。