  We show that gated bilayer graphene zigzag ribbons possess a fast and a slow
edge, characterized by edge state velocities that differ due to non-negligible
next-nearest-neighbor hopping elements. By applying bosonization and
renormalization group methods, we find that the slow edge can acquire a sizable
interaction-induced gap, which is tunable via an external gate voltage V_{g}.
In contrast to the gate-induced gap in the bulk, the interaction-induced gap
depends non-monotonously on the on-site potential V.
