Looking here, and assuming all books allowed, though you're not interested in looking at the new Beserker, I recommend.
For a dwarf:
1: Dwarven Weapon Proficiency
2: Bludgeon Expertise (You'll want this for the avalanche maul) or Enduring Mountain (tribal feats are excellent if everyone buys in)
4: Improved Defenses (your ref and will will be low. This helps a little) or Bludgeon Expertise
6: Cunning Stalker (if you're off and about charging random people away from your party) or Mark of Storm (While it doesn't support an avalanche hammer, it's doubtful that your DM will give one to you. A lightning weapon is a lot more common, and a slide 2 on hit is excellent for making enemies stick to your defender and setting up your next charge.)
8: Deadly draw (if mark of storm) or Blood Cousin's Tribe (if people've gone enduring mountain) or Reckless Charge
For a Goliath
1: Goliath Greatweapon Prowess
then, as above. Goliaths don't need superior weapons with greatweapon prowess.
For a Half-Orc
1: Bludgeon Expertise or Heavy Blade Expertise (depending on your style and whether or not you can request a badge of the beserker)
2: Weapon Focus or Enduring Mountain
4: Toughness or Improved Defenses
6: Cunning stalker or as above
8: Thirst for Battle
For a Minotaur
As half-orc, but 8 should be bloodied ferocity
For a Warforged
As half-orc, but 6 should be warforged tactics, and 8 reckless charge or go the mark of storm route
To generalize
Taken from the charop guide:
Accuracy bonuses - A Barbarian's attacks are dealing a lot of damage pretty much by default; a bigger priority for you is making sure those attacks actually get to connect, especially considering you don't have a native accuracy-boosting feature and you usually only get one shot at landing them.
Damage bonuses - While Barbarian attacks are pretty damaging already, it never hurts to pack more punch on your hits, you being a Striker and all.
Mobility enhancements - One of the best ways to accomplish the above two priorities is by charge optimization, since there are items to enhance accuracy and damage for chargers. Throw in some mobility to generate the necessary space to charge early and often, and you have yourself a character.
Defense bonuses - While Barbarian Agility combined with raising Strength and Dexterity aggressively should cover the majority of your defenses nicely by default, some investment in making yourself tougher to hit is certainly not a waste of time, especially on the non-AC defenses side.
Miscellaneous - After those basic tenets are covered, you pretty much have free rein with any feat slots you may have left over. I personally prefer to optimize initiative (and thus get my blows in faster) or power recovery (to get another go at using good powers) of, if you have the room, both.
For a strcon barb, especially one with a non-trivial investment into con, you'll be really hurting. Your first feat, however, should almost always be iconic or accuracy-related. +1 and a bennie is the best way to inflict the best status condition there is: dead. However, before accuracy is the signature weapon of the barbarian. As a charger, you functionally have 2 enchantments to choose from in the heroic tier: Vanguard (+1d8 damage while charging) works on any melee, but a fullblade is your best bet for the increased accuracy. Whiffing a howling strike sucks. Or Avalanche Hammer Mordenkrad, for a lovely +1[W] on charging. With an avalanche mordenkrad, your charger will be doing 5d6 (+1d6 because horned helm) brutal 1... at will. It's therefore important to choose between weapon types as early as possible.
If you were a strdex barb (very much recommended, You don't need a secondary con to take advantage of rageblood) I would instead recommend a vanguard gouge, so you can take advantage of a fighter multiclass for surprsing charge and spear expertise. +scaling to damage from the expertise,+1[W] with surprising charge with combat advantage (gained from cunning stalker) makes you ... remarkably scary.
If you want your DM to throw dice at you, I recommend mounted combat and a dire boar. Dice will be thrown, however.
Enduring Mountain is something I've got experience with in my own games. It grants a remarkable amount of health per surge used if everyone buys in and helps make up for a lackluster leader. Or for the depressing healing demands an almost naked strcon barb imposes.
Improved defenses is generic, but useful. When you have slots open up, it's worth retraining into superior X (or just grabbing superior will on top of it.) Grabbing superior reflexes is also nice on the combat advantage charging chassis for that excellent first-round combat advantage.
Best Answer
The Celts Campaign Sourcebook was published in 1992 for AD&D 2nd Edition, and as our OP found, it had some sort of feat system. So it must have been invented before then. Since Dragonlance acted as some kind of testbed for TSR in some regards, I am looking at these adventure rules for evidence that can pin it down.
DLA2 - Dragon Knight (TSR #9285) was printed 1990 and has "Special Skills" for characters that follow the Dragon Knight class on page 59, granting (bonus) proficiencies, special maneuvers, and immunities:
DL13 - Dragons of Despair (TSR #9176) was printed 1986, and its Appendix does not refer to anything akin to feats. However, the bestiary does describe things that nowadays would be handled under a feat keyword, for example, page 33 says (in plaintext!):
As a result, the first precursors of feats must have entered D&D between 1986 and 1990.