GUI 是个 acronym, acronym 就是那种恰好是那种能发出来一个单词的音的缩写词.https://www.merriam-webster.com/dictionary/acronym
"When speaking to a familiar audience, no-one spells out acronyms that have vowels helping them feel like a real word. NASA, GIF, SWAT, NATO. However spelled out acronymns are also popular not just when we can't make a real-sounding word (FBI, SVG, HTML) but even when there are some vowels that would make it feasible (CIA, DEA, GOP).
For technical audiences that work with a thing every day, use the colloquial form to sound like you belong. I was super old when I found out that in some places everybody calls SQL "seequel". For GUI, when talking to tech folks say gooey. But G U I is not "improper", just longer." --引自 reddit 的回答.