from the wonderful Web Page Design for Designers – Symbolism
“One of the most important aspects of navigation, and interface design generally, lies in an understanding of graphic symbolism.
If you have had a good art college training, you will probably have been introduced to the theoretical concepts behind symbols and logotype design.
Capturing the literal or abstract essence of a company identity and making a visual representation of it in the form of a symbol or trade mark is something a graphic designer has to do all the time.
Designing icons and navigational devices for computer programs requires exactly the same skills and, for those readers who have not had the advantage of such a background, I will give a brief introduction.”
Italics mine. I had not made this connection before, but it rings very true and provides a clue to why so many icons fail….