  (Abridged) We present the results of high S/N long-slit spectroscopy with the
Multiple Mirror and the SAO 6-m telescopes, optical imaging with the Wise 1-m
telescope and HI observations with the Nancay Radio Telescope of the very
metal-deficient (12+log(O/H)=7.64) luminous (M_B=-18.1) blue compact galaxy
(BCG) HS 0837+4717. The blue bump near lambda4650, characteristic of WR stars
is detected in the central supergiant HII region, as well as the barely seen
red bump at lambda5808. The derived number of WR stars in the region of the
current starburst is ~1000. Evidence for fast motions in this region is also
seen as broad, low-contrast components in the Ha, Hb and strong [OIII] lines.
While the extinction of the narrow emission lines from the supergiant HII
region is low, the very large Balmer decrement of the broad components suggests
that the part of current starburst is highly obscured by dust. Abundance ratios
X/O for X=Ne, Ar, S, Fe and Cl in the supergiant HII region are in good
agreement with the mean values of other BCGs. Nitrogen, however, is
overabundant by a factor of ~6. This implies an unusually efficient N
enrichment in HS 0837+4717, and probably, a non-typical evolution scenario. The
Ha-line Position--Velocity diagrams for directions approximately along the
major and minor axes reveal disturbed motions of the ionized gas. The SW part
of the major axis P--V diagram looks like a rotation curve, with V_rot ~50--70
km/s at r=4.3 kpc. Its NE part displays, however, strong deviations, indicating
either counter-rotation, or strong outflow/supershell. The overall BCG
morphology is highly disturbed. With a "double-nucleus" structure, disturbed
velocities of ionized gas, and the very high power of the starburst this
suggests a possible explanation of the object as a recent merger.
