What is Fictitious Name?

Legal Definition
A counterfeit, feigned, or pretended name taken by a person, differing in some essential particular from his true name, (consisting of Christian name and patronymic,) with the implication that it is meant to deceive or mislead. But a fictitious name may be used so long or under such circumstances as to become an "assumed" name, in which case it may become a proper designation of the individual for ordinary business and legal purposes. See Pollard v. Fidelity F. Ins. Co., 1 S. D. 570, 47 N. W. 1060; Carlock v. Cagnacci, 88 Cal. 600, 26 Pac. 507.
-- Black's Law Dictionary