The verb know serves to express many different states of knowledge in English which other languages use multiple verbs to express. For example, the French language uses two different verbs savoir and connaître to express two different states of knowledge. Savoir expresses knowledge of facts and figures, whereas connaître expresses knowledge of people.
However, this all purpose verb in English was not always as such. If we trace the verb back to Old English and Anglo-Saxon literature, we meet know in the form cnawan and also another verb witan from which is derived the words wit, nitwit, dimwit, outwit, and wise. Witan seems to assume most of the functions of know.
For example, in the Old English translation of Apollonius of Tyre, we read:
“Nate ic hwæt he is ne hwanon he is, ac gif ðu wille witan hwæt he is, axsa hine, forðam þe gedafenað þæt þu wite (1).”
“I don’t know who he is or where he’s from, but if you want to know who he is, ask him, since you have a right to know.”
In this quotation, witan signifies knowledge of a person and facts about them such as where they are from. It is an interesting example of this word. An interesting study would be to look for when cnawan began to replace witan in English and finally end up surpressing it to become the modern know, but that is a study for another day, though my inclination is to say the change took place mostly in the late 1400’s and early 1500’s when wit meaning a clever or funny saying first came into currency.
As to the origins of these two words, let us deal with them separately. Cnawan is related to French connaître, Latin gnoscere, and Greek γιγνώσκω from a Proto-Indo-European root in gno-.
Witan is more interesting. It is related to Afrikaans weet and Ancient Greek οίδα. Οίδα is the perfect form of wίδω (hence Latin video) meaning ‘I see.’ So to know in Ancient Greek is to have seen. This makes a lot of sense because that is really what knowledge and science is: having seen things and having made observations. The Proto-Indo-European root for this word is wit/d-.
1. The Old English Apollonius of Tyre. ed. Peter Goolden. Oxford University Press 1958. p. 24 sect. XV 2-5.