Etymology

Formed on the Gmc noun represented by OE lēoma, OS liomo, OIcel ljómi ‘beam, ray, radiance’ (< PGmc *leuxmōn); no such verb is recorded in OE, and this is presumably what motivates TGD to derive ME lemen from the attested ON wk. 2 v., cp. OIcel ljóma ‘to gleam, shine’. But other authorities (inc. OED, MED) regard the ME v. as a (recent) derivation on ME leme n. < OE lēoma. 

PGmc Ancestor

*leuxmōn

Proposed ON Etymon (OIcel representative)

 ljóma ‘to gleam, shine’
(ONP ljóma (vb.))

Other Scandinavian Reflexes

Far ljóma, Icel ljóma, Norw ljoma, Sw dial ljömma

OE Cognate

lēoma (n.) 'ray of light, beam, radiance, glare'

Phonological and morphological markers

Summary category

CC1c

Attestation

Predominantly N and E and alliterative in ME, with a handful of exceptions (inc. the KG Seinte Marherete); MnE N and Sc. dial.

Occurrences in the Gersum Corpus

Gaw 591, 1119, 1137 etc.; Cl 1273, 1486; WA 553, 3335, 4910 etc.

Bibliography

MED lēmen (v.2) , OED leam (v.1) , HTOED , EDD leam (sb.1 and v.1) and Dance leme, de Vries ljóma, Mag. ljómi