参考
cānkǎo · HSK 4
refer to
📖 参 cān (consult) + 考 kǎo (examine) = consult and examine = refer to
参 means to participate or consult; 考 means to test or examine. Together 参考 literally means to consult-and-examine, i.e. to refer to a source. Same 考 as in 考试 kǎoshì (exam).
考 — old 老 (top) + 丂 phonetic
Originally written like 老 ('old'), 考 depicted an elderly person with long hair leaning on a cane, and the two characters were once interchangeable. Over time 考 specialized to mean 'deceased father' and later 'to examine, test, investigate,' with the bottom 丂 hinting at the sound.