My setting includes aliens called Riders, little lizard-caterpillar thingies that have a symbiotic relationship with animals. I’m trying to come up with a snappy name for the animals. They’re these big dumb quadrupeds, roughly similar to bovines, but with digging tusks for eating roots. Riders use the animals for transportation/remembering how to get somewhere (Riders have terrible spatial memory), finding food, protection against pack predators, and companionship. The animals need Riders to deal with powerful lone predators (by a method I won’t detail here), and Riders also treat their injuries and keep them clean of parasites. Riders can communicate some commands, like “remember this location” or “hold still for now,” but the animals aren’t smart enough to say much back. Usually it’s just intelligent species that get an English name in this setting (the Builders, the Scholars, etc.), but I feel like these animals need a name because they’re so closely linked to the Riders. I’ve been calling them “Bond-beasts,” but I feel like I’m missing a better term. (“Companions” sounds like a euphemism, and “Diggers” underplays their importance.)
If I were far away from a finished rough draft, I'd just use a simple thesaurus, find the best candidate, and use it as a placeholder and maybe change it later. For your example, I came up with 'Brawns' (get it - you've got the brawn, I've got the brains...), BOBs (short for beasts of burden), and 'Juments', a word I never heard before that means beast of burden.
I actually like "Bond-beasts", for some reason. It sounds unusual, nearly alien, but very descriptive. Like a word born out of necessity to describe a thing that's very integral to the Riders' biology and culture. Often, things that have been around forever, don't have complicated names, because nobody ever sat down and tried to make one up. The names arose in the dark of the past. If you simply leave away the hyphen, it sounds fine. The word is as unfamiliar to us, the readers, as the entire concept of always being dependent on another animal is.
I know that you seem to want English words, but..... I always default to thesaurus and translate apps when I get stuck. My Thesaurus list: bovine oxen grazer steer beast kine cattle bullock From Translate (I picked a couple at random): language - Bengali Bōbhā'ina balada cāraṇa hāla dharā jantu kā'ina gabādi paśu balada language - Xhosa inyama yenkomo iinkomo idlelo lawula irhamncwa inkomo iinkomo inkunzi yenkomo I sort of like "Balada" and "Inkomo." Mash them up a bit and I get "Balink."
I know the feel. I'm actually just about to post a thread very similar to this one, for exactly the same reason. Anyway, I gather we're looking for a term implying "something that carries you, that you rely on for survival," and I agree it feels like there should be a fitting one. All I can think of right now is "steed" or "mount." Life Mount? Life Steed? Carrier guide... thing? I dunno, I'll try thinking about it some more.