Hartmann is a German surname. It is less frequently used as a male given name. The name originates from the Germanic word, "hart", which translates in English to "hardy", "hard", or "tough" and "Mann", a suffix meaning "man", "person", or "husband". The name Hartman, distinguished by ending with a single "n", is generally the result of the anglicisation of names that occurred with the emigration of persons from German-speaking to anglophone nations in the 18th, 19th and early 20th century.
https://en.wikipedia.org/wiki/Hartmann