1. These are now distinct words and are only distantly related. A
council is an administrative body or meeting, and its members are
councillors.
Counsel is advice given formally and often professionally;
counsel or
a counsel is a barrister or other legal adviser. A
counsellor is someone who gives professional advice, especially on personal and social matters; in American English
counselor is also a courtroom lawyer.
2. Note that in Britain a member of the
Privy Council, the body of advisers appointed by the Queen, is a
Privy Counsellor.
3. Only
counsel can be used as a verb, meaning 'to give advice to'; it has inflected forms
counselled,
counselling.