Etymology

Probably formed within English as an aphetic form of ylikeness from the native form of the Gmc base of lyke (adj.) + suffix. OED3 also cautiously compares OIcel líkneski (neut)., líkneskja (fem.) 'shape, form, image, etc.', formations on the same base, with the early use of aphetic forms in N sources (also noted by MED). Thus it is impossible to rule out ON input, but the form is better explained as a native development.

PGmc Ancestor

*(ga)līka-

Proposed ON Etymon (OIcel representative)

líkr ‘like, alike’; cp.  líkneski (neut)., líkneskja (fem.) 'shape, form, image, etc.'
(ONP glíkr (adj.); líkneski (sb.) (n.)., líkneskja (sb.)(f.))

Other Scandinavian Reflexes

OE Cognate

Phonological and morphological markers

Summary category

CCC2

Attestation

Aphetic forms are attested early in Nhb OE (licness- in the Lindisfarne Gospels). MED has widespread citations, beginning with Orrm (and incl. Gower and Lydgate), of which N texts perhaps feature disproportionately. 

Occurrences in the Gersum Corpus

WA 382, 1709, 3679

Bibliography

MED līknes(se (n.) , OED3 likeness (n.) , HTOED , de Vries líkneski n., líkneskja f., Mag. líkneski h., líkneska kv.; see further lyke (adj.).