But we do know!

Not true. The "words" with which specific species call some others has been determined and can be observed, so "we would never know" is false.

My dog has specific vocalizations for known guests, unknown guests, my spouse, and rabbits.

We study animal communication a lot. We know when many different animals have a noise or communication for "human." Bees have different dances to describe arbitrary locations, so they could also have a specific dance for "that jerk over there with the mesh helmet."

What other species think about me is none of my business.