Lose the thread [closed]

I just found out that the idiom “to lose the thread” exists in English. This surprised me a bit because I read a lot in English (both fiction and non-fiction, old and modern) but I've never encountered the phrase in this exact form. (I've always expressed the idea as “losing one's train of thought”.) Literal equivalents exist in other languages, including German and my native Spanish. My question is: do you consider this idiom common? Additionally, do you use it? Is it colloquial, formal, or neither especially?

Solution 1:

If the thread has to do with a narrative, then the expression is not uncommon.

Lose the thread

Cease to follow the sense of what is said. For example, It was such a long story that I soon lost the thread. This expression uses thread in the sense of “something that connects the various points of a narrative.” [Mid-1900s]

(Source: Dictionary.com)

You could perhaps use this when you lost your train of thought, but it is much more likely to be used in a desultory conversation (where the conversationalists lost the thread of the conversation) or in a narrative in a story (where the author lost the thread of the plot).

Here is another usage of a narrative thread:

The older you get, the easier it is to see how the threads of life become the whole cloth of character. When you are consistent in the patterns you create and the passions you pursue, the fabric is strong and stable; when you aren’t, the fabric frays. Thus, the machine of life stitches the narrative thread each day.

(Source: https://thenarrativethread.com/)

This idea of a narrative thread works because both life (and a story) can only be presented one moment at a time. If one loses the thread, then life either becomes unraveled or the story becomes hard to follow.

Solution 2:

The saying is an analogy with losing the thread of yarn or thread used to weave cloth or to sew material. If the thread is lost, by breakage, by becoming enmeshed in the weaving process, or by being sewn in the wrong place, the process stops, effort has to be made to recover the process, and irretrievable damage may have been done.

Similarly, if the thread of an argument, a narrative, or an exposition is lost, there is confusion, delay, and perhaps the destruction of the process or a failure to reach conclusion.

The idiom would be widely understood in Britain, perhaps from the days when British cotton and wool mills dominated global cloth manufacture.