Meaning of valgus: A deformity involving oblique displacement of part of a limb away from the midline.
Doubt: Why is genu valgum knock knees? The knees (genu) are displaced towards the midline!
Answer: It's not the knees we consider during the deformity... It's the relationship of distal part with the proximal part at a joint.
Mnemonic: L in vaLgum is for Lateral displacement.
(Conversely, varuM is medial displacement.)
That's all!
Hate the inaccurate naming.
-IkaN