1580s, "fitted by accomplishments or endowments;" 1590s, "affected by some degree of restriction or modification;" past-participle adjective from qualify (v.). By 1886 and into mid-20c. as a British English euphemism for bloody or damned.
To be competent is to have the natural abilities or the general training necessary for any given work ; to be qualified is to have, in addition to competency, a special training, enabling one to begin the work effectively and at once. He who is competent may or may not require time to becomequalified; he who is not competent cannot become qualified, for it is not in him. [Century Dictionary]