Why is it called "טלטול מן הצד"?

Question

Most things that can't be moved on Shabas (or yom tov) can be moved if the following two criteria hold:

1. One is moving them by means of another object.
2. The purpose of moving them is not for their own sake but for the sake of some permitted object.

_{An example frequently given is leftover crumbs on a table. If they can't permissibly be moved by hand (as is sometimes the case) then they can nonetheless be swept up with a squeegee or knife, so long as the purpose is a clean table rather than collecting the crumbs. (Note, though, that the rules are more complicated than I can include here and, in particular, not everyone agrees that the case of crumbs on a table falls under this exemption. As always, consult your rabbi with any practical questions.)}

The term for this type of permitted moving, dating back to the g'mara, is "טלטול מן הצד", literally "moving from the side".

Why is it called that? Moving something via another object doesn't make the motion more "from the side". Does it mean you're moving the object from your side? But you always move things from your side, as your hands are on your sides. Or does it perhaps mean you're moving the object from its side? But using another object instead of your hand doesn't mean you're approaching the forbidden object from any particular side. Or what does it mean? What's the understanding of this phrase as applied to this permitted action?

Answer 1

1. Ba'al HaMaor (Shabbat, Perek Kirah)

שכל איסור והתר שמטלטל האיסור מצד ההיתר נקרא טלטול מן הצד

Every case of something forbidden [to move] and something permitted where he moves the forbidden thing by way of the permitted thing, is called tiltul min hatzad.

The above is my translation; my sense is that Ba'al HaMaor translated min hatzad as 'by way of', and tiltul min hatzad is short for 'moving it by way of something permitted.'

2. Rashi (Shabbat 43b)

מן הצד - כלאחר יד

Min hatzad - in an atypical manner [lit. backhandedly].

It seems to me that Rashi understands min hatzad metaphorically, to mean 'in a roundabout way', in the sense of coming at something from the side rather than approaching it directly.

This is further indicated by his comments on Shabbat 47b where he explains why binyan min hatzad (building 'from the side') is so called:

מפני שאינה תקועה ומהדקה בחוזק קרי לה מן הצד כלומר ע"י שינוי

Since it isn't attached and fastened securely, he calls it 'min hatzad', meaning in an unusual manner.

Note the word כלומר in his comments, which often indicates that Rashi is giving a less literal interpretation.