Filter/map/reduce are ubiquitous ideas from the functional world, which in turn are ideas drawn from mathematics. Math has pre-existed many of our programming constructs, so in that sense, nothing was really invented as such.
To me, what LINQ offers is a very nice orthogonal DSL that allows programmers to express these thoughts. The underlying constructs are universal, but one could argue that LINQ itself was invented. LINQ was apparently guided by category thinking [0], which makes it fairly elegant, but in terms of expressiveness it is probably similar to SQL. It's all set theory underneath anyway. Unlike SQL however, LINQ does force the SELECT statement to the very end of the query expression, which makes IDE auto-complete work better due to avaiable context. :)
I first had the realization that most data manipulation operations on list-like or table-like objects were actually just glorified set operations (and there was a certain universality to them regardless of query language syntax) when I read this quote [1]: "The turning point was a conversation with Erik Meijer. He told me how categorical thinking guided him in designing LINQ, and explained how category theory brings out a simple relationship between various kinds of databases. The diagram below comes from a paper he wrote on this. It turns out that so-called No-SQL databases are in a categorical sense co-SQL databases."
[0] https://queue.acm.org/detail.cfm?id=2024658
[1] https://www.johndcook.com/blog/applied-category-theory/