firm 2 
(fûrm)
(fûrm)n.
1. A business enterprise.
2. An unincorporated business, particularly a partnership.
3. The name or designation under which a company transacts business.
[Italian firma, from firmare, to ratify by signature, from Medieval Latin firmāre, from Latin, to confirm, from firmus, firm; see dher- in the Appendix of Indo-European roots.]