That monster's name does not mean what you think

Many of fantasy gaming's monsters originate from mythic, legendary, folkloric and literary sources. In many cases their portrayal in mangled in the process. For example, a number of monsters have name which had completely different meanings before being co-opted by fantasy gaming.

See, Gary Gygax and friends read a lot of old fiction but were not particularly educated in the context of what was read. They would see a word and, not knowing the actual definition, would wrongly assume the meaning from that context alone.

• Athach (and ettin) was a synonym for giant. Gygax and co used it as a name for a monster they made up.
• Lich originally meant a corpse, animated or not. Pulp fiction popularized the term. One story used it in reference to a necromancer who had reanimated their own corpse. Gygax and co read that story and, not knowing the definition of "lich", mistook it to refer to an undead spellcaster. It also has a martial variant called the death knight (or in Pathfinder, the graveknight).
• Troll refers to ugly creatures of Scandinavian folklore, ranging from dwarves to giants. Of course, Gygax and co squandered this rich history and just copied a one-note monster from a Poul Anderson story.
• Wight originally meant a living creature (especially supernatural) or an unlucky person. It was used by Tolkien in The Fellowship of the Ring as part of a conjunction: "barrow-wights" (literally, "grave-men"). Gygax and co, again, did not know the meaning of the word and mistook it to mean an undead creature.

For those of you that would prefer to respect the original etymology, for whatever reason, I may provide a few suggestions. Or devise your own at your leisure.

• Giants are referred to with adjectives like "two-headed," "three-armed," "shaggy furred" and so forth rather than trying to make up a unique name every time.
• "Lich" is a generic term for reanimated corpses, often used as an affix in monster names. The intelligent kind--often but not always with their soul bound into an external object, place or creature (sword, armor, phylactery, dungeon, familiar, etc)--are generally known by simple, obvious names. Such names usually consist of an adjective relating to death and a noun referring to profession. Adjective examples: death, grave, zombie, skeletal, undead, lich, etc. Noun examples: knight, master, champion, lord, warrior, mage, etc. More poetic titles include "Lords of Sorrow."
• "Troll" becomes a generic term for giants and humanoids that are not humans or demi-humans. For example, goblins and orcs are collectively referred to as trolls.
• "Wight" becomes a generic noun used in the names of monsters. For example, a "forge wight" (ref. Creature Collection Revised) is a small fire elemental that lives in a forge, while a "barrow-wight" is a reanimated corpse that guards barrows.