The name of the company is a pun on The Dunwich Horror, a short story written by H.P. Lovecraft in 1928.
The following is based on Fallout 3 cut content and has not been confirmed by canon sources.
According to cut dialogue from the original version of the Point Lookout quest The Dark Heart of Blackhall, the company was owned by Richard Dunwich, the brother of Constance Blackhall. The dialogue also mentions both Dunwich and Blackhall's shared "obsession with the occult", hinting that the presence of the obelisk underneath the building was not unintentional.
End of information based on Fallout 3 cut content.