What's a tuple in normal English?

A tuple in mathematics is a sequence of numbers (n1, n2, n3).

In databases, a tuple is a single row of data from a table.

What is a tuple in normal everyday English, or where does the word come from? Is there a concrete real-life object from which this word is derived? WordNet does not have a definition.

The word derives from the extended series of single, double, triple, quadruple, quintuple,..., where named multiples beyond five are generally words that end in "tuple". The natural (Latin-derived) words peter out pretty quickly, and mathematics needs more terms than a simple bipedal meat unit can easily memorize, so the term "n-tuple" was coined. Computer science took that ball and ran with it, dropping the "n-" altogether.

In other words, "tuple" has no meaning in everyday English.

Nothing. The word tuple is back-formed from Latinisms like quintuple, and it is only used in technical contexts. The average English speaker has never heard the word, and it has no meaning outside of the context of mathematics or software engineering.