The question is about 问讯 (I am learning Buddhism/dharma in Chinese.)

为什么合掌鞠躬叫"问讯"？

或是说：

为什么现在的"问讯"不是用讲的？

"问"和"讯"都是动词吗？还是动词+名词？
依香光莊嚴解釋：
在漢語的構詞上，問訊是由「問」與「訊」二個同義詞所組成的詞彙。
「問」是動詞，意思是「恤問」。
「訊」是動詞，意思是「詢問」。

如果「訊」作名詞，在非佛教場合也還是可以用的。如：打聽消息。

現在的"問訊"也還是有用講的，但通常只在人少的時候。當很多人同時向佛或法師表達恭敬時，沒辦法大家都講，所以就只有身體的動作。

問訊 is composed of two synonyms, 問 and 訊.
Both are verbs, meaning "comfort and ask".

If 訊 is a noun, it can still be used in non-Buddhist cases.
Such as: to inquire about something.

Nowadays, 問訊 can still be used orally, but usually only in the cases of 2 or 3 people. When many people express respectful to the Buddha or the masters at the same time, they cannot speak all together. So they only show the body movements.