Proper noun
Hackmann (plural Hackmanns)
A surname from German.
Hackmann and Friedrich make clever use of what might be called an accidental experiment. Source: Internet
W Hackmann, Seek & Strike: Sonar, anti-submarine warfare and the Royal Navy 1914-54 (HMSO, London, 1984) By 1918, both France and Britain had built prototype active systems. Source: Internet