Etymology

Interpreted as a formation on ME dank ‘wet, damp’, which is often referred to an ON dank- as represented by OIcel dǫkk ‘?hollow, pit, ?swampy tract, fen’, Sw dank ‘moist place in field’, Sw dial dänka ‘to moisten’, etc. (see Bj., MED) because the presumed PGmc root *ðank- is not otherwise recorded outside Scandinavia, but Norse derivation is uncertain (see OED). 

PGmc Ancestor

*ðank- 

Proposed ON Etymon (OIcel representative)

dǫkk ‘?hollow, pit, ?swampy tract, fen’
(ONP dǫkk (sb.))

Other Scandinavian Reflexes

Icel dokk, dökk, Norw dokk, Sw dial dank, dakk; dänke 

OE Cognate

Phonological and morphological markers

Summary category

BB1c

Attestation

Both the v. and the adj. (n.) are rare in ME, and confined to alliterative poetry (usually in collocation with dew), mainly from the N/EM (the original dialect of Lenten ys come (Hrl 2253) (no. VIII of the ‘weltliche Lieder’ in Böddeker ed. 1878) is classed as NWM by Brook (1933: 60). Used as a v. in MnE Lan. dial.

Occurrences in the Gersum Corpus

Gaw 519

Bibliography

MED danken (v.) , OED dank (v.) , HTOED , EDD dank (adj. and v.), Dance dokande, Bj. 233, de Vries dǫkk, Mag. dokk (1), Orel *ðankō