And since this was just the one whale, the researchers are unsure whether there are more copy-cat killer whales in the wild.
Orcas can say "hello", "bye-bye" and "one-two-three", while the voice doesn't make a ideal mimicry, but sounds impressively identifiable.
In the wild, killer whales live in pods and are known to have different dialects, but there has been intense debate in the scientific community around how this came to be.
"History will record that in the second decade of the third millennium, a killer whale uttered the word "hello" to a human," Luke Rendell, Lecturer in Biology at the University of St Andrews, which also assisted in the study.
Call said that their team thought it would be really convincing to present killer whales with something that is not in their repertoire - and in this case, "hello" is not what a killer whale would say.
After listening to the human or whale sound, Wikie was requested to reproduce them by her trainer saying "do this".
From the water, a high-pitched squeak calls out "hello" but the sound is not coming from a human, it's a whale.
"One of the main things that fired the evolution of human intelligence is the ability to have social learning, to imitate, and to have culture", said Abramson.
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Wikie was taught to copy novel sounds and words from both another killer whale - her own three-year-old calf, Moana - and by humans.
Orcas have previously been shown to make vocalizations that they learned from their mothers and from other groups, a skill that served as a basis for the new experiments. Indeed, Wikie's reproduction of the word "hello" sounds practically human.
"But we were surprised by how close it was".
Researchers from institutions in Germany, UK, Spain and Chile in their journal Proceeding of the Royal Society B state that the 14-year-old Wikie was first trained to copy actions performed by another ocra on giving signals by humans. The orca speech is the equivalent of us blowing our noses, so the fact that Wikie was able to mimic human words with such accuracy is an interesting phenomenon.
The researchers used software to figure out how similar the orca sound was to the sound that the orcas had heard, whether it was the sound of another orca or of a human.
In recordings of the experiment, Wikie takes several stabs at "hello". While the sounds may be accurate, there's no evidence that Wikie actually understands what any of it means.
Killer whales have been noted to express themselves in dialects: calls and accents specific to each pod.
Diana Reiss, an expert in dolphin communication and professor of psychology at Hunter College, City University of NY, welcomed the research, noting that it extends our understanding of orcas' vocal abilities, with Wikie able to apply a "copy" command learned for imitation of actions to imitation of sounds.