It is known that Guilford coined the term, but the concept is much older. What did people in Freud's time call it? Genius? innovation? Something else?
Let me open this by saying that it's not clear to me that Guilford coined the term, as the Google n-gram viewer shows use well before 1950:
Freud wrote an essay on creative writers (and day-dreaming) in 1908 but he does not talk of creativity as a noun/concept in itself at least in the English translation. Likewise Jung wrote a fair bit about the "creative impulse", but like in the case of Freud he doesn't seem much concerned how comes people are creative but just why they start to manifest it outwards as art. Another similar term Jung used was the "creative fire". At my level of understanding, the reason for this lack of concern in the psychoanalytic tradition is that they explained (away) the source of the creative process as the unconscious. And once they get to the unconscious as the ultimate explanation, all effort for further understanding what goes under that seems to stop, and the their efforts are directed at understanding the manifestations of the unconscious. It's a bit like saying that you can't understand God, but you can study his works. I'm probably exaggerating that, but part of the issue surely is methodological; Jung and Freud did not apply (or even outright rejected) a systematic scientific method.
The stated motivation of Guilford's work on creativity was that he thought the IQ tests were only good at discriminating elementary school performance, but not good for discriminating what he called "creative potential". In "Creativity: Yesterday, today, and tomorrow" Guilford credits Catharine Patrick with the first experimental studies of creativity; she wrote several papers from 1935 to 1941 with "Creative thought" in their title. Guilford says Patrick attempted to systematically test the anecdotal evidence of Graham Wallas (1926) related in his book titled "The art of thought". There doesn't seem to be an on-line record of Patrick's earliest (1935) paper on the topic. Her 1937 "Creative thought in Artists" and 1941 paper "Whole and Part Relationship in Creative Thought" are available on-line. Neither paper uses "creativity" as a term in their text, so in this narrow sense Guilford was the first to use the term in the nascent field.
The premise of this question is mistaken. As early as 1875, A W Ward referred to Shakespeare's "poetic creativity". (Source: Oxford English Dictionary, under "creativity"). That was eight decades before the 1950s and two decades before J P Guilford was born.