調子
ちょうし · choushi · JLPT N3 · noun
tone
🎻 調子 = tune (調) + noun suffix (子): how well-tuned you are today
調 means to tune or adjust, as in 調整 (adjustment). 調子 started as a musical word for pitch or key, and later came to mean the state you are in. 調子がいい means you're in good form; 調子が悪い means you're out of sorts.
子 — pictograph of a baby/child with arms out
子 began as a pictograph of a swaddled infant with a large head and outstretched arms, originally meaning 'baby' or 'child.' From there it broadened to 'son,' 'offspring,' and a respectful suffix for masters like 孔子 (Confucius). It also became one of the twelve earthly branches.