jargon.artrocity.com
New Hacker's Dictionary the Jargon File v 4.4.6
[RPI, from off-by-one and the Obi-Wan Kenobi character in Star Wars] A loop of some sort in which the index is off by one.
1. Common when the index should have started from 0 but instead started from 1.
2. A kind of off-by-one error. See also zeroth.