Among Romans it was the custom for a man seeking office to wear a shining white robe. Since the name for such a color was candidus (whence our "candid"), the office seeker came to be called candidate. In our ceremonies the custom is reversed: the candidate is clothed after his election instead of before.
- Source: 100 Words in Masonry
An applicant for admission into Masonry is called a candidate. The Latin candidatus means one who is clothed in white, candidis vestibus indutus. In ancient Rome, he who sought office from the people wore a white shining robe of a peculiar construction, flowing open in front, so as to exhibit the wounds he had received in his breast. From the color of his robe or toga candida, he was called candidatus, whence the word candidate. The derivation will serve to remind the Freemason of the purity of conduct and character which should distinguish all those who are candidates for admission into the Order.
The qualifications of a candidate in Freemasonry are somewhat peculiar. He must be free-born-under the English Constitution it is enough that he is a Freeman, under no bondage, of at least twenty-one years of age, in the possession of sound senses, free from any physical defect or dismemberment, and of irreproachable manners, or, as it is technically termed, under the tongue of good report. No atheist, eunuch, or Woman can be admitted. The requisites as to age, sex, and soundness of body have reference to the operative character of the Institution. We can only expect able workmen in able-bodied men.
The mental and religious qualifications refer to the duties and obligations which a Freemason contracts. An idiot could not understand them, and an atheist would not respect them. Even those who possess all these necessary qualifications can be admitted only under certain regulations which differ under the several Masonic Constitutions.
- Source: Mackey's Encyclopedia of Freemasonry