I didn't research who'd chosen these names, and it doesn't really matter that much (compared to anyone's favorite atrocity) — but it just pains me to see this in a high-quality open-source Haskell library:

"Data" is plural already — singular is datum.
... I well understand, fixing this would entail a breaking change, deprecations and major version bump.
Perhaps something to consider for version 1.0.0.0 ?