How did 'folding' semantically shift to mean 'reply'?

Question

I seek more details and other opinions than Cerberus's answer that cited Lewis & Short on what notions underlie folding and replying.

As to why folding (back) came to mean uttering (back), I imagine the figurative sense "to roll something over in the mind" was expanded to rolling something over in a conversation, inspecting it by talking about it.

How can 'roll over in mind' broaden to mean 'roll something over in a conversation' then to 'reply'? I've never heard of the VP 'roll something over in a conversation' in English; it doesn't feel intuitive.

Etymonline proclaims that

replicare "to repeat, reply," literally "to fold back,"

originates

from re- "back, again" (see re-) + plicare "to fold" (from PIE root *plek- "to plait")

p 1785 on Oxford Latin Dictionary (2012 2 ed) doesn't expound the semantic shift. I marked the entry with a red line.

Answer 1

It seems to me you could ask the same question about return and retort. Apparently the idea that an argument or question is like a ray or missile directed at you, and you turn it around or bend or fold its trajectory when you make a reply, underlies these words. (Note how, for example, the English word retort simultaneously refers to a reply in an argument and a chemical flask with a bent neck.)

In the Oxford Latin Dictionary entry, you already see uses like this:

• radii soli replicantur (sunrays are reflected [= bent back] by the earth: Seneca, Naturalis Quaestiones, 2.10.3)
• vestigium suum replicat (he turned back, returned: Apuleius, Metamorphoses 4.19)

It seems natural to me to extend this to a conversation between people, where utterings, or thoughts and ideas, are sent back and forth.

Please note that the meaning reply in general (not just in the courtroom) may be a Middle Latin development, and the OLD, which explicitly excludes Middle Latin, would in that case not be the right resource to consult.

Answer 2

A modern equivalent of the same semantic shift would be monitor speakers which are often called 'fold-back' speakers, because they 'fold back' the sound to the musicians on stage, this is almost like an echo, which could be viewed as a "reply" to the person making the noise.

Answer 3

Regarding the shift from "folding" to "returning" Sp. Llegar, wiktionary has some interesting comments: "The semantic shift over time from "to fold" is also found in some other Romance cognates, and may be linked to the idea of folding sails when arriving at a port, especially in Iberian Romance where naval tradition was strong. Compare Portuguese chegar; however cf. also Romanian pleca (“to leave”), with the opposite meaning, possibly because there the word was associated with folding up tents and leaving."