In Ars Magica (4e or 3e ? I don't remember. I have the French translation by Descarte, I think it was of the version before WotC reprinted it), there was some rules about liches. They said that the word "lich" was a deformation of a celtic word for "life". I found it interesting, given that "golem" had the same origin (deformation of a hebraic name for life, they were also supposed to carry a phylactery with "golem" written on it, and if you deleted one letter, it became the word for "death" and the golem was destroyed. At least that's what I've heard, I'm unable to verify it first-handely).