跟
gēn · HSK 1
with
👣 跟 = 足 (foot) + 艮 (phonetic gèn) — follow at the heel
The foot radical 足 carries the meaning of heel/following, while 艮 lends the sound. From literal 'heel' it extended to 'follow', then to the grammatical 'with/to/from' — going along with someone.
跟 — foot radical 足 + 艮 (phonetic)
A semantic-phonetic compound. The left side 足 (foot) gives the meaning, since 跟 originally referred to the heel of the foot. The right side 艮 supplies the sound. From 'heel' it extended to 'follow behind,' and in modern Chinese it also works as 'with' or 'and.'