недобор

By surface analysis, не- (ne-, negating particle) +‎ Proto-Slavic *doborъ (“intake, collected amount”).

недобо́р • (nedobór) m (obsolete)

1. amount of debt or tax that remains to be collected

   Synonym: (colloquial) баки́я (bakíja)

• недосъбра́н (nedosǎbrán, “not yet collected”)

• “недобор”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Sofia: Bulgarian Academy of Sciences, 2014
• “недобор”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Chitanka, 2010
• Nayden Gerov (1899) “недобо́ръ”, in Рѣчникъ на Блъгарскꙑй язꙑкъ. Съ тлъкувание рѣчи-тꙑ на Блъгарскꙑ и на Русскꙑ. [Dictionary of the Bulgarian language]‎^[1] (in Bulgarian), volume 3, Plovdiv: Дружествена печꙗтница "Съгласие.", page 258