Flatten table into Association Thread where each cell is an association from its column and row header

Question

Let's say I have a table in Mathematica like so:

Where the first row is the header, and first column is also a header (similar to a multiplication table). ie S_AS_A = Es; S_BS_A = ss_sigma;

The layout for this list is like so:

{
{
{header row},
{"row name1",row item 1, row item 2, etc...}
{"row name 2", row item 1, row item 2, etc...}
}
}

How do I flatten this table into an association thread like so:

Answer 1

Maybe it works with

energies = {{{"Column1", "SA", "SB", "SC", "SD", "PxA", "PxB", "PxC", "PxD", "PyA", "PyB", "PyC", "PyD", "PzA", "PzB", "PzC", "PzD"}, {"SA", "Es", "sssigma", 0., "sssigma", 0., "-spsigma", 0., 0., 0., 0., 0., "spsigma", 0., 0., 0., 0.}}}[[1]];
Normal@AssociationThread[
 Flatten@Outer[
   Times,
   energies[[1, 2 ;;]],
   energies[[2 ;;, 1]],
   1
   ],
 Flatten@energies[[2 ;;, 2 ;;]]
 ]

{("SA")^2 -> "Es", "SA" "SB" -> "sssigma", "SA" "SC" -> 0., "SA" "SD" -> "sssigma", "PxA" "SA" -> 0., "PxB" "SA" -> "-spsigma", "PxC" "SA" -> 0., "PxD" "SA" -> 0., "PyA" "SA" -> 0., "PyB" "SA" -> 0., "PyC" "SA" -> 0., "PyD" "SA" -> "spsigma", "PzA" "SA" -> 0., "PzB" "SA" -> 0., "PzC" "SA" -> 0., "PzD" "SA" -> 0.}

Alternatively, you may use Thread@Rule instead of Normal@AssociationThread (this should be also a bit faster).