I'm fairly certain it started with an "S" as well.
Now I realize that you subsequently realized that the word didn't start with S, but I would add this to Todd Wilcox's answer suggesting bridge:
According to Wikipedia's article on Bar form, the beginning of the Abgesang was known by the Meistersinger as the Steg, which in modern German denotes a particular type of bridge. Wikipedia further claims (without evidence) that this is the source of the modern sense of "bridge" as an element of musical form.
Bar form is an AAB form in which the last phrase of the repeated A section is frequently identical to the last phrase of the B section (Rundkanzone). Therefore, the first part of the B section is heard only once.
The A section was typically shorter than the B section, and the two instances of the A section were sung using different words. The A section wasn't necessarily half the length of the B section, but one may indulge in a bit of anachronistic comparison by noting that making the A section 8 measures long and the B section 16 measures long yields something very much like the classic 20th-century 32-bar popular song form, with the "middle eight" or bridge occupying precisely the same position as the Steg as a point that offers contrast where repetition is expected. Indeed, the Wikipedia article on Rundkanzone linked above notes that Rundkanzone may be described as ABABCB or AABA, with the latter being the usual schematic description of the 32-bar form.
The "Bar" in Bar form isn't the same "bar" in 32-bar form. It couldn't be, because Bar form was established several centuries before the development of modern metrical notation using bar lines. Wikipedia says
The word Bar is most likely a shortening of Barat, denoting a skillful thrust in fencing. The term was used to refer to a particularly artful song – the type one composes in songwriters' guilds.