The preterite-presents are verbs whose present tenses look like the past tenses of strong verbs. This resemblance isn't an accident: they descend from old Proto-Indo-European stative verbs, which normally developed into the past tense of the Germanic languages. The preterite-present verbs are an exception to this development, remaining as independent verbs. For example, the first-person present of "witan" ("to know") originally meant "I have seen", referring to the state of having seen, and by implication "I know". At some point well before Old English, these verbs were given their own past tenses by tacking on weak past endings, but without an intervening vowel. This lack of an intervening vowel then led to alternations in the consonants, and sometimes vowels as well.