Name for a set of pairs of elements that equalise two functions? Is there an established name for this $eql$ function?
$$\operatorname{eql}(f, g) = \{\ (x, y)\mid f(x) = g(y)\ \}$$

I've discovered through Reddit (see Bill's link) that this is called the pullback:
$$pb(f, g) = \{\ (x, y) \mid f(x) = g(y)\ \}$$
The equalizer is:
$$eql(f, g) = \{\ x \mid f(x) = g(x)\ \}$$
But we can define each in terms of the other:
$$pb(f, g) = eql(f \circ \pi_1, g \circ \pi_2)$$
$$eql(f, g) = pb(f, g) \cap pb(id, id)$$
