Etymology

From OE þencan, this v. is widely attested in Gmc., cp.  OIcel þekkja, Go þagkjan, OFris thenza, thanka, OS thenkian, OHG denkan. It is possible that unassibilated ME present tense forms in /k/ show input from the ON form (Krygier 2000), but Scandinavian influence is not generally adduced and OED3 maintains the older idea (see esp. Luick) that /k/ variants continue the stem-form proper to OE syncopated 2 and 3 sg. pres. ind.

PGmc Ancestor

*þankjan-

Proposed ON Etymon (OIcel representative)

þekkja 'to perceive, recognize, know'
(ONP þekkja (1) (vb.))

Other Scandinavian Reflexes

Far tekkja, Icel þekkja, Norw tekkja, ODan tække, OSw þäkkia

OE Cognate

 þencan 'to think, imagine, consider (etc.)'

Phonological and morphological markers

[absence of palatalization of */k/] (possibly diagnostic)

Summary category

CCC2

Attestation

Spellings clearly denoting a stop /k/ are fairly common throughout ME, esp. in the later period, when <ch>-spellings are much rarer and confined to the S and W of England, esp. the SW and SWM (see further LALME dot maps 298, 300, 302).

Occurrences in the Gersum Corpus

Gaw 487, 534, 1680 etc.; Pe 22, 370, 1151; Cl 138, 304, 711 etc.; Pat 294; Erk 225; WA 672, 1121, 2425 etc.

At WA 1640, the A MS reads <hopis>.

Bibliography

MED thinken (v.2) , OED3 think (v.2) , HTOED , HTOED , Dance þenk, de Vries þekkja (1), Mag. þekkja, Bj-L. tenke, Orel *þankjanan, Kroonen *þankjan-, AEW ðencan