deformity in which a bone or joint is twisted outward from the center of the body; form of club-foot, 1800, from Latin valgus "bandy-legged, bow-legged, having the legs bent outward." Said to be probably related to Sanskrit valgati "to move up and down," Old English wealcan "to roll, move to and fro" (see walk (v.)), perhaps on the notion of "go irregularly or to and fro" [Tucker]. "Yet the main characteristic of 'bow-legged' is the crookedness of the legs, not 'going up and down' or 'to and fro'" [de Vaan] and there are phonetic difficulties. A classical word used in a different sense in modern medicine; also see varus.
foot deformity in which the feet are extroverted, so that the inner ankle rests on the ground, while the sole of the foot is more or less turned outwards, 1800, from Latin varus "bent, bent outwards, turned awry, crooked," specifically "with legs bent inward, knock-kneed," a word of uncertain origin (see vary).
If the original meaning was 'with the legs opened', varus might be compared with vanus and vastus, and reflect *wa-ro- 'going apart, letting go'. In any case, none of the other etymologies proposed seems plausible. [de Vaan]
The use of classical varus and valgus, which denoted deformities of the legs, in modern medicine to describe deformities of the feet, was criticized by learned writers (see "Edinburgh Medical and Surgical Journal," July 1838).