How does 'versus' metaphorise plowing in Ancient Rome?

Question

[ Etymonline :] from Latin versus "a line, row, line of verse, line of writing,"
from PIE root *wer- (3) "to turn, bend" (see versus). The metaphor is of plowing, of "turning" from one line to another (vertere = "to turn") as a plowman does.

How does the metaphor of plowing explain the semantic shift from the PIE root to Latin? I can understand that the act of scrutinising each line of writing can be metaphorised by plowing each row, but then how does proceeding from one line to the next connect with turning in plowing? A reader would descend ocularly from the current line of writing to the next line; it sounds strange to describe this as 'turning' from one line to the next.

Answer 1

I think it is best to interpret "turning to the next line" simply as "moving to the beginning of the next line". There is no reason to expect that words would shift their meaning in a perfectly rational manner.

That said, some ancient texts were indeed read a way you (and many others) find strange: first line from left to right, the next one from right to left, then from left to right, and so on. Alternating directions allows one to easily find the beginning of the next line. This kind of writing is known as boustrophedon. The term itself comes from ploughing context. See the linked Wikipedia article for more details.