  With a luminosity similar to that of Milky Way dwarf spheroidal (dSph)
systems like Sextans, but a spatial extent similar to that of ultradiffuse
galaxies (UDGs), Andromeda (And) XIX is an unusual satellite of M31. To
investigate the origin of this galaxy, we measure chemical abundances for
AndXIX derived from medium-resolution (R$\sim$6000) spectra from Keck
II/DEIMOS. We coadd 79 red giant branch stars, grouped by photometric
metallicity, in order to obtain a sufficiently high signal-to-noise ratio (S/N)
to measure 20 [Fe/H] and [$\alpha$/Fe] abundances via spectral synthesis. The
latter are the first such measurements for AndXIX. The mean metallicity we
derive for AndXIX places it $\sim2\sigma$ higher than the present-day stellar
mass-metallicity relation for Local Group dwarf galaxies, potentially
indicating it has experienced tidal stripping. A loss of gas and associated
quenching during such a process, which prevents the extended star formation
necessary to produce shallow [$\alpha$/Fe]--[Fe/H] gradients in massive
systems, is also consistent with the steeply decreasing [$\alpha$/Fe]--[Fe/H]
trend we observe. In combination with the diffuse structure and disturbed
kinematic properties of AndXIX, this suggests tidal interactions, rather than
galaxy mergers, are strong contenders for its formation.
