Etymology

Formed on ME knag(ge ‘knob, spur, peg’, a word with analogues (with the same senses) in the continental Scandinavian languages, cp. Sw knagg, Dan knag, Norw knag, knagge, and also in WGmc, cp. MLG knagge. These forms are usually related to OIcel knakkr ‘little chair, high stool’, LG knacke ‘a peg’ (on the possible further connections of which see e.g. Torp-Falk 48–9, Orel s.v. *knakkaz ~ *knakkō). The existence of WGmc analogues supports the prevailing view that the ME word is more likely to be cognate with the ON than derived from it.  

PGmc Ancestor

*knaʒʒ-

Proposed ON Etymon (OIcel representative)

knakkr ‘little chair, high stool’
(ONP knakkr (sb.))

Other Scandinavian Reflexes

Norw knag, knagge, Dan knag, Sw dial knagg, knagge; Icel knakkur, Norw knakk

OE Cognate

Phonological and morphological markers

Summary category

BBB2ac

Attestation

Recorded in ME by MED as a v. (pp.) only at Gaw 577 and 1540(?a1400) DT(Htrn 388) (plus two instances spelt gnagg- from eastern texts); the noun (MED s.v. knag(ge n.) is also rare in ME, and recorded in MnE Sc. and N dial. 

Occurrences in the Gersum Corpus

Gaw 577

Bibliography

MED knaggen (v.) , OED knag (v.) , HTOED , EDD knag (sb.1), Dance knaged, Bj. 247, Hellquist knagg, Nielsen knag, Falk-Torp knag, Torp NnEO knagge, Orel *knaʒʒaz