Any book of zemiros whether it's a siddur, birchon, or what have you divides the zemiros between the three meals. Sometimes the rationale is obvious as with the tikkunim which are written for each meal. Sometimes they seem arbitrary like Kah Ribbon. My question is twofold:
I have not found a source.
I would like to suggest that from the subject matter of the zemiros some could possibly be assigned to Friday night as follows.
“Menucho vesimcho” mentions the sixth day, “ki leshisho kol beruim veomdim”.
“Mah Yedidus” speaks about the evening “mai’erev mazminim”.
“Mah Yofis” cites being ready before Shabbos “nechonim mib’oid yom”.
“Yom Shabbos Kodesh Hu” mentions the two angels that accompany us home from shul Friday night “umalach kail ya’ane boruch”
and “Yom Ze LeYisroel” talks about the completion of creation on the sixth day “beshaishes kiliso meleches olomim”.
“Tzomo Nafshi” seems to be a preface to “Nishmas” and might be assigned to Shabbos day.
“Koh Ribon Olam” seems not to be assignable.
“Koh ecsof noam” has a phrase about waiting for Shabbos kodesh to arrive “shomrei umetzapim Shabbos kodesh” and so can be justified for Friday night.
I could find not reason to assign the Shabbos day zemiros, except perhaps the mention of the “Lechem Haponim” (which were divided between the kohanim on Shabbos day) in “Ki Eshmero”.
This is my own thoughts. Perhaps the composer of each song composed it specifically for the meal it is sung at.
I have no source for this:
The division of zemirot between night and day is fairly arbitrary, but the essential issue is to separate the songs sung on Friday night, as Shabbat comes in, from the songs sung at Shalosh Seudos / Havdalah, when Shabbat goes out.
This is to prevent confusion later in the week, if one is away from the Jewish community and needs to remember when Shabbat is. Keeping the songs separate helps prevent "off by one day" errors.
