The ELKO field was originally suggested in 2005 by D. V. Ahluwalia (then, under the name Ahluwalia-Khalilova) and D. Grumiller. The name comes from the acronym of the original German term Eigenspinoren des LadungsKonjugationsOperators, designating spinors that are eigenspinors of the charge conjugation operator.
ELKO quantum fields ﬁelds describe spin-1/2 fermions with mass dimension one. Since the field has a mass dimensionality mismatch with standard model matter fields it was suggested as a dark matter candidate. As a result of their scalar-like mass dimension they differ significantly from the mass dimension 3/2 Dirac fermions.
A slightly old reference is a 2013 preprint. The results following equation (102) need revision as the indicated integral does not vanish. There are now strong indications that using Elko a mass dimension one field of spin-1/2 fermions can be constructed to secure locality and Lorentz covariance. An up-to-date review is now available as an e-print 
- D.V. Ahluwalia and D. Grumiller. Spin-Half Fermions with Mass Dimension One: Theory, Phenomenology, and Dark Matter. Journal of Cosmology and Astroparticle Physics, 2005:012, 2005.
- D.V. Ahluwalia, C.Y. Lee, D. Schritt, and T.F. Watson. Local Fermionic Dark Matter with Mass Dimension One. Arxiv preprint arXiv:0804.1854v4, 2008
- M. Dias, F. de Campos, J. M. Hoff da Silva. Exploring Elko typical signature. Physics Letters B, 706 (2012) 352. DOI:10.1016/j.physletb.2011.11.030
- D. V. Ahluwalia. On a local mass dimension one Fermi field of spin one-half and the theoretical crevice that allows it. http://arxiv.org/abs/arXiv:1305.7509
- Dharam Vir Ahluwalia. A Lorentz covariant local theory of fermions with mass dimension one. http://arxiv.org/abs/1601.03188