Old English bisceop "bishop, high priest (Jewish or pagan)," from Late Latin episcopus, from Greek episkopos "watcher, overseer," a title for various government officials, later taken over in a Church sense, from epi- "over" (see epi-) + skopos "watcher," from skeptesthai "look at" (see scope (n.1)). Given a specific sense in the Church, but the word also was used in the New Testament as a descriptive title for elders, and continues as such in some non-hierarchical Christian sects.
Late Latin episcopus in Spanish became obispo. Cognate with Old Saxon biscop, Old High German biscof. The chess piece (formerly archer, before that alfin) was so called from 1560s.