维基有，最终是参考这个：

The letter ‘Q’ was chosen as the class prefix because the letter looked beautiful in Haavard’s Emacs font. The ‘t’ was added to stand for “toolkit”, inspired by Xt, the X Toolkit.

https://web.archive.org/web/20190923193951/https://my.safaribooksonline.com/0131872494/pref04
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FROM 123.115.161.*