Crom Cruaich means "Crooked-mound." He has other
variants - the most common being Crom Dub "Crooked-black" but also Cenn Cruaich
"Head mound."
Crom Cruaich comes from a Celtic *Crombo-croucio-
while Crom Dub from *Crombo-dub[u]o- and Cenn Cruaich from *Quenno-croucio-. It
is noteworthy that Cenn Cruaich has its exact Brythonic match in the British
placename Penno-croucion, now Penkridge. Perhaps Cenn Cruaich was an imported
Brythonic deity (a genius locus of Pennocroucion?) brought by British
immigrants, which might account for his malignant status in Irish myth (as a
foreign divinity).
Crom is heavily associated with Lugnasad, which
has the alternate name "Crom's Sunday." Crom is still remembered in Irish
folklore (some whisper that he is still half-worshipped!), even making it into
Irish-American Robert E. Howard's Conan series as Conan's chief god (despite
Schwarzenegger's accent in the movies, Howard envisioned Conan and his
Cimmerians to be Proto Celts!). Crom is associated with the harvest, like Lug,
and may represent a dark side of Lug, as Crom is not so much adored as
feared.
-C. Gwinn