Fear has almost always been a 4th-level wizard spell in D&D. Primarily the weird thing about it has been how much the range/area of effect changed in different editions.
Fear: The Wand effects all creatures within a cone-shaped area eminating from it 6" outwards to a base 3" wide. All within it must make their saving throw as against magic or be panicked and flee.
In the boxed-set LBBs of OD&D, fear does not appear as a spell; it only appears as the effect of a magic wand, as shown above (quote from Vol-2, p. 34). It's the first effect given in the game as a smallish and close-range cone effect, 6" long maximum. This cone area is re-used for the wand of cold and wand of paralization [sic] which immediately follow on the same page of Vol-2. In Supplement-I Greyhawk, this wand effect then inspires a new magic-user spell:
Fear: This spell operates as if the user were employing a Fear Wand. All those not saving vs. fear react as follows: They immediately attempt to flee, or get as far away from the user as possible, with a 50% chance that they will drop any weapons they had in hand when struck by the Fear spell. Duration: 6 turns (movement or melee as applicable). Range 24”.
Here's the rub: The spell says that it works as a fear wand, but that's contradicted by the 24" range for the spell. Is the wand's 6" cone area extended out to 24", for a titanic area of effect? Or is the same-sized cone generated at any point within the 24" range (very hard to rationalize)? This seems like a clear mistake/oversight. Note that as written, there are actually no spells in OD&D with a cone-shaped area of effect (there are wands, breath-weapons, and the horn of blasting, but absolutely no spells described as cone-shaped). Also, someone added the new "50% drop weapons" side-effect which I think is a fiddly Sup-I'ism of which I'm not fond.
Swords & Spells
Fear: 24" (Range), 4" diam. (Area Effect), 6 (Turn Duration).
As we've said before, Gygax's Swords & Spells miniature combat for D&D has a comprehensive listing of magic range, area, and durations. In some few places this includes effective errata for some spells, and fear is among the examples. As you can see above, the small cone area is deleted, with a circular 4" diameter area of effect allowed in the 24" range (just like fireball, et. al.). I think that's about the most reasonable fix if we want to keep the long range for the spell. In fact, I kind of wish that Gygax had used the same fix for the other short-range, wand-inspired spells ice storm and cone of cold (in 1E). However, this interpretation was not kept in any later edition of D&D. (Like many Sup-I additions, it doesn't appear in B/X at all, so now we skip to AD&D.)
AD&D 1st Edition
Area of Effect: 6” long cone, 3” diameter at end, 1/2’ at base
Components: V, S, M
Casting Time: 4 segments
Explanation/Description: When a fear spell is cast, the magic-user sends forth an invisible ray which causes creatures within its area of effect to turn away from the spell caster and flee in panic. Affected creatures are likely to drop whatever they are holding when struck by the spell; the base chance of this is 60% at 1st level (or at 1 hit die), and each level (or hit die) above this reduces the probability by 5%, 1.e. at 10th level there is only a 15% chance, and at 13th level 0% chance. Creatures affected by fear flee at their fastest rate for the number of melee rounds equal to the level of experience of the spell caster. The panic takes effect on the melee round following the spell casting, but dropping of items in hand will take place immediately. Of course, creatures which make their saving throws versus the spell are not affected. The material component of this spell is either the heart of a hen or a white feather.
Now in AD&D the fear effect has reverted radically back to the same very short area as the Original D&D wand. The range has switched from the maximal 24" category to 0 here, and the area is the 6" cone emanating from the caster (which seems to put the caster in proximity with the dangerous opponent, and makes it possibly hard to avoid catching friends in the beam). Also that aggravating drop-weapons detail is blooming into another unique rule that requires a varying-probability roll for each creature affected (ugh).
AD&D 2nd Edition
Area of Effect: 60-ft. cone, 30-ft. diameter at end, 5-ft. at base
When a fear spell is cast, the wizard sends forth an invisible cone of terror that causes creatures within its area of effect to turn away from the caster and flee in panic. Affected creatures are likely to drop whatever they are holding when struck by the spell; the base chance of this is 60% at 1st level (or at 1 Hit Die), and each level (or Hit Die) above this reduces the probability by 5%. Thus, at 10th level there is only a 15% chance, and at 13th level no chance, of dropping items. Creatures affected by fear flee at their fastest rate for a number of melee rounds equal to the level of experience of the spellcaster. Undead and creatures that successfully roll their saving throws vs. spell are not affected.
The material component of this spell is either the heart of a hen or a white feather.
Mostly the standard copy-and-paste job for 2E spells. The range remains 0, and the area the old short cone effect.
D&D 3rd Edition
Necromancy [Fear, Mind-Affecting]
Level: Brd 3, Sor/Wiz 4
Components: V, S, M
Casting Time: 1 action
Range: Close (25 ft. + 5 ft./2 levels)
Duration: 1 round/level
Saving Throw: Will negates
Spell Resistance: Yes
An invisible cone of terror causes living creatures to become panicked. They suffer a –2 morale penalty on saving throws, and they flee from the character. A panicked creature has a 50% chance to drop what it’s holding, chooses its path randomly (as long as it is getting away from immediate danger), and flees any other dangers that confront it. If cornered, a panicked creature cowers.
In 3E, this is basically similar to the preceding AD&D effect. The drop-weapons chance is at least simplified to a flat 50% here (as in Sup-I). The "cone" area expands with the level, and elsewhere is specified to have a terminal width the same as the length. For example: a 12th-level wizard has a 55 ft. long cone, 55 ft. wide at the far end (about the same length as in AD&D, but twice as wide).