Derived from earlier kneipen, from Middle Low German knīpen, from Old Saxon *knīpan, from Proto-West Germanic *knīpan. Cognate with Dutch knijpen.
The form with -f- is an adaptation to the High German consonantism, for which there may have been rare antetypes in northern dialects of Central German, but which was chiefly artificial. Kneipen remained predominant until the earlier 19th century, but was somewhat informal. The more standard-looking kneifen then fully established itself in written German and displaced kneipen by the mid-20th century.
kneifen (class 1 strong, third-person singular present kneift, past tense kniff, past participle gekniffen, auxiliary haben)
| infinitive | kneifen | ||||
|---|---|---|---|---|---|
| present participle | kneifend | ||||
| past participle | gekniffen | ||||
| auxiliary | haben | ||||
| indicative | subjunctive | ||||
| singular | plural | singular | plural | ||
| present | ich kneife | wir kneifen | i | ich kneife | wir kneifen |
| du kneifst | ihr kneift | du kneifest | ihr kneifet | ||
| er kneift | sie kneifen | er kneife | sie kneifen | ||
| preterite | ich kniff | wir kniffen | ii | ich kniffe1 | wir kniffen1 |
| du kniffst | ihr knifft | du kniffest1 du kniffst1 |
ihr kniffet1 ihr knifft1 | ||
| er kniff | sie kniffen | er kniffe1 | sie kniffen1 | ||
| imperative | kneif (du) kneife (du) |
kneift (ihr) | |||
1Rare except in very formal contexts; alternative in würde normally preferred.