My information regarding the Portsmouth surname is a little speculative but here goes anyway. I am actually researching the Surname Crow in Hackney Middlesex and have recently obtained information on a Baptism in Hackney. This was for a Jennet Portsmouth Crow born Oct 18th 1780. Parents John and Elizabeth Crow. The middle name seemed an unusual one and I wondered if this could have been the Mothers maiden name ??
If anyone researching the name Portsmouth, and finds a Crow connection I would really appreciate hearing from them.