prompt, n. = 'an intellectual or emotional stimulus to artistic creation; inspiration'

[Jonathan Lighter]

Nothing in OED covers this, "prompt," n. 2, def. 2a covers only sensory
stimuli that elicit some behavior from the unconscious.

1999 Harry Ricketts _Rudyard Kipling: A Life_  (rpt. N.Y.: Carroll & Graf,
2001) 275: The prompt for the poem was a letter in early December from
"Bobs"....

2004 Francis O'Gorman _Victorian Poetry: An Annotated Anthology_ (Malden,
Mass.: Blackwell, 2004) 166: Tennyson’s prompt for the poem was a report in
the Times…recounting what rapidly became known as one of the British Army’s
most infamous errors.

Frankly, I find this usage creepy because it suggests to me that Kipling and
Tennyson were reacting like chimps to a behavioral "cue." They couldn't help
themselves!  And, no, the authors are not sneering at either poet.  (Cf.
phrases like "what prompted his reaction.")

JL

-- 
"If the truth is half as bad as I think it is, you can't handle the truth."

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