I think there's a good reason for the function keyword to be abbreviated.

We know that when people read lines of text, they pay a lot of attention to the beginning and the end and comparatively less attention to the middle. One result is that lines with common prefixes tend to blur together. To get around this, you want the reader to encounter the unique portion of the line ASAP, which makes it desirable that any kind of necessary prefix be brief.

Upshot is you want the function signature to be what you see as you scan down the left side of the page, so it does make sense to keep the function keyword particularly concise.