  We report $\alpha$-Cu$_2$V$_2$O$_7$ to be an improper multiferroic with the
simultaneous development of electric polarization and magnetization below $T_C$
= 35 K. The observed spontaneous polarization of magnitude 0.55 $\mu$Ccm$^{-2}$
is highest among the copper based improper multiferroic materials. Our study
demonstrates sizable amount of magneto-electric coupling below $T_C$ even with
a low magnetic field. The theoretical calculations based on density functional
theory (DFT) indicate magnetism in $\alpha$-Cu$_2$V$_2$O$_7$ is a consequence
of {\em ferro-orbital} ordering driven by polar lattice distortion due to the
unique pyramidal (CuO$_{5}$) environment of Cu. The spin orbit coupling (SOC)
further stabilize orbital ordering and is crucial for magnetism. The
calculations indicate that the origin of the giant ferroelectric polarization
is primarily due to the symmetric exchange-striction mechanism and is
corroborated by temperature dependent X-ray studies.
