aficionado
Concise Oxford English Dictionary © 2008 Oxford University Press:
aficionado /əˌfɪsjəˈnɑːdəʊ, -ˌfɪʃjə-/
▶noun (pl. aficionados) 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 part. of aficioner ‘become fond of’ used as a noun, based on L. affectio(n-) (see affection).
'aficionado' also found in these Oxford entries:

