So.. for people rating rangers as much less common than fighters... what does your average trapper count as? Personally I see "someone who knows the woods" as a more common archetype than "someone who is a professional combatant", although I understand if things are coming from a more city-centric world view.
In terms of 5e? Well, there are some human NPCs in the back of the Monster Manual. I suppose you could try to track them to that. Seems like this might be Minigiant's way. Makes sense. A trapper as "Scout" makes sense.
I would probably look at the Backgrounds: 2 skills, 1 Tools, maybe do away with the extra Language, give equipment. Guild Artisan is fairly ready made, even though "Furriers & Trappers" does not appear on the Guild Business list. Outlander also seems a natural choice.
Trapper
Skills: Replace "Insight & Perception" from Artisan or "Athletics & Survival" from Outlander with "Nature Lore & Tracking" (or Survival?).
Tools: Herbalism Kit...or if you want to get more creative: "Trappers Tools" [use with successful Dex. check for "Setting Traps"].
Language: n.a.
Equipment: a wrought iron "bear trap", 50' rope (for snare/tripwire making), a small knife [ for "skinning", d2 damage if used as weapon], a normal set of clothes with fur-lined water-resistant ("oiled") hooded cloak.
If you want to do 'em up more class like, throw in Proficiency with Light armor and hand axe, dagger, spear, and light crossbow.
Rangers are, indeed, "wilderness warriors" specifically trained in the skills necessary for existing/surviving in borderlands and wilderness beyond "civilized/settled" areas
and (here's where the ranger and the trapper deviate)
finding/tracking/hunting/battling/defeating the recurring and/or imminent threats of that region when-/wherever they find them.
When the orcs raiding party moves into the valley on the other side of the hill, the trapper will slink away back through the woods. Whether in hopes of getting back to the outpost to warn them, or (less honorable individuals) maybe just in hopes of getting out of Dodge entirely ("let the outpost deal with it, themselves, if they can").
The ranger, on the other hand, possibly with some form of notification- like a tune on a horn, bird calls, smoke signals, etc...- to others of his ilk, hightails it
into that valley. She does recon. She assesses and harries the force and learns about the full situation as best she can. Is this a scouting party for a larger force? Is this a hunting party that will leave in a day/not even going to the outpost? IS this a raiding party hoping to murder and pillage the ill-manned trade-post over the next hill? Is this a group of demon-worshipping cultist orcs who are going to try to raise Gruumsh from the long-abandoned druid's circle of standing stones that no one at the outpost even knows exist in this valley? If possible, she lay traps, uses stealth, ranged weaponry, and her special "against orcs" combat training to decisively and concisely take out the raiding orcs by the handful or
entirely, if its within their power to do so.
I tend to think of and describe them as the "Int-base/Skill Fighters" (using their skills, wits, and guile) vs. normal Str-base/Trained Fighters, the "Con-base/Wild Fighters" a.k.a. Barbarians, "Wisdom-base/Divine Fighters" a.k.a. Paladins). Part of their skill set includes long kept, passed down, and/or secret lore lost or forgotten by most other "fighting men" (or society as a whole) and so includes skill with using magical items and [perhaps, eventually] a bit of minor magic/spellcasting.
[When I get to play 5e, rangers will default to a non-casting variant and not be spellcasting until later levels...if at all.]