  Thick discs are nearly ubiquitous components of the discs of present-day
galaxies. It has been proposed that a fraction of their stars has been
accreted. Here, we aim to find whether accretion of satellites is the main
thick disc formation mechanism. To do so, we observed a sample of eight nearby
edge-on galaxies with the MUSE integral field unit at the VLT. Six of the
galaxies have a distinct thick disc. We derived thick disc velocities and
velocity dispersions for the galaxies in our sample. We devise a formalism to
estimate the fractions of retrograde material in the thick discs by using
kinematical maps and thin/thick dis decompositions. None of the galaxies in our
sample shows strong evidence for retrograde material at large distances from
the centre. Including those found in the literature, there are seventeen thick
discs with studied kinematics, with only one showing unambiguous signatures of
retrograde material. Literature numerical studies of dynamical friction allow
us to estimate that at the current cosmic time about one in six mergers for
which the stars of the accreted galaxy ended in a thick disc were retrograde.
This is in tension with the observed fraction of 1/17 of galaxies with a partly
retrograde thick disc. We conclude that satellite accretion is not favoured by
observations to be the main thick disk formation mechanism.
