  In this work we characterise the properties of the object SDSS
J020536.84-081424.7, an extended nebular region with projected extension of $14
\times 14$ kpc$^{2}$ in the line of sight of the ETG Mrk 1172, using
unprecedented spectroscopic data from MUSE. We perform a spatially resolved
stellar population synthesis and estimate the stellar mass for both Mrk 1172
($1 \times 10^{11} M_{\odot}$) and our object of study ($3 \times 10^{9}
M_{\odot}$). While the stellar content of Mrk 1172 is dominated by an old
($\sim 10$ Gyr) stellar population, the extended nebular emission has its light
dominated by young to intermediate age populations (from $\sim 100$ Myr to
$\sim 1$ Gyr) and presents strong emission lines such as: H${\beta}$, [O III]
${\lambda}{\lambda}$4959,5007, H${\alpha}$, [N II]
${\lambda}{\lambda}$6549,6585 and [S II] ${\lambda}{\lambda}$6717,6732. Using
these emission lines we find that it is metal-poor (with $Z \sim$ 1/3
$Z_{\odot}$, comparable to the LMC) and is actively forming stars ($0.70$
M$_{\odot}$ yr$^{-1}$), especially in a few bright clumpy knots that are
readily visible in H${\alpha}$. The object has an ionised gas mass $\geq 3.8
\times 10^{5}$ M$_{\odot}$. Moreover, the motion of the gas is well described
by a gas in circular orbit in the plane of a disk and is being affected by
interaction with Mrk 1172. We conclude that SDSS J020536.84-081424.7 is most
likely a dwarf irregular galaxy (dIGal).
