[ əˌfɪsjə'nα:dəʊ , -ˌfɪʃjə- ]
■ noun ( plural ~s ) a person who is very knowledgeable and enthusiastic about a particular activity or subject.
Origin
C19 (denoting a devotee of bullfighting): from Sp., 'amateur', past participle of aficioner 'become fond of' used as a noun, based on L. affectio(n-) (see affection ).