刻
kè · HSK 2
to carve
⏰ kè = a 'quarter-hour' carved on the clock; also means to engrave
刻 originally meant to carve or engrave (knife radical 刂 on the right). It became a time unit because ancient water clocks were marked with carved notches — each notch = one kè, roughly 15 minutes.
刻 — knife radical 刂 + 亥 (phonetic)
A semantic-phonetic compound. The right side 亥 supplies the sound, while the knife radical 刂 on the right gives the meaning, since 刻 originally referred to carving or engraving with a blade. From 'to carve' it extended to marking time notches on a sundial, hence the modern sense of 'a moment' or 'quarter hour'.