キョウ, わき, わけ
armpit, the other way, another place, flank, supporting role
JLPT0 G7 S10 F1806
Effectively a variant form of 脅# (one's side), with the 肉 flesh element repositioned, and emphasizing the physical points the *armpits* and the *sides/flanks* → *side*. Compare 胳 and 亦.
[Full Kanji Etymology List]