ma·jor / ˈmājər/ • adj. 1. important, serious, or significant: the use of drugs is a major problem. ∎  greater or more important; main: he got the major share of the spoils. ∎  (of a surgical operation) serious or life-threatening: he had to undergo major surgery. 2. Mus. (of a scale) having an interval of a semitone between the third and fourth degrees and the seventh and eighth degrees. Contrasted with minor. ∎  (of an interval) equivalent to that between the tonic and another note of a major scale, and greater by a semitone than the corresponding minor interval. ∎  (of a key) based on a major scale, tending to produce a bright or joyful effect: Prelude in G Major. ∎  (of a triad) having a major third as the bottom interval. 3. of full legal age. 4. Logic (of a term) occurring as the predicate in the conclusion of a categorical syllogism. ∎  (of a premise) containing the major term in a categorical syllogism. 5. Brit., dated (appended to a surname in some schools) indicating the elder of two brothers.• n. 1. an army officer of high rank, in particular (in the U.S. Army, Air Force, and Marine Corps) an officer ranking above captain and below lieutenant colonel. 2. Mus. a major key, interval, or scale. ∎  (Major) Bell-ringing a system of change-ringing using eight bells. 3. a student's principal subject or course of study. ∎  a student specializing in a specified subject: a math major. 4. a major world organization, company, or competition: it's not unreasonable to believe someone can win all four majors. ∎  (the majors) the major leagues. 5. a person of full legal age. 6. Logic a major term or premise.7. Bridge short for major suit. • v. [intr.] (major in) specialize in (a particular subject) at a college or university: I was trying to decide if I should major in drama or English.

major1 officer below the rank of lieutenant-colonel. XVII. — F. (short for sergent-major sergeant-major, orig. a much higher rank than now) — L. mājor; see next. Also in m.-general (XVII), earlier sergeant-m.-general (XVII). — F. major-général, where major is sb. and général adj.
So major-domo chief official of a household. XVI. Earliest forms maior-, mayordome — (partly through F. majordome) Sp. mayordomo, It. maggiordomo — medL. mājor domūs (domūs, g. of domus house) highest official of the royal household under the Merovingians.

major2 greater. XVI. — L. mājor (:- *māgjōs) compar. of magnus great (see MAGNITUDE).
So majority † superiority, state of being of full age XVI; greater number or part XVII. — F. majorité — medL. mājōritās.