There’s a video[1] of Karpathy recounting an email correspondence he had with with Bahdanau. The email explains that the word “Attention” comes from Bengio who, in one of his final reviews of the paper, determined it to be preferable to Bahdanau’s original idea of calling it “RNNSearch”.
[1] https://youtu.be/XfpMkf4rD6E?t=18m23s