I am pretty sure that those who are studying German must have encountered the following verb and noun:
das Abkommen (Agreement, pact)
and
abkommen (to deviate)
I am pretty sure the above noun derived from the verb abkommen but I cannot correlate it with the verb! How come the meaning has changed just simply by turning the noun into the verb?
According to the Grimms the verb abkommen was formerly also used in the meaning of "to agree with somebody on something":
Endlich ist mit einem abkommen so viel als überein kommen, fertig werden, sich vertragen, vergleichen. Grimm
This was similarily used like the modern verb übereinkommen which also exists as a noun Übereinkommen (agreement, convention).
Therefore the noun Abkommen indeed is a direct derivation from the verb abkommen where one of the meanings of the verb is lost today.
Interestingly it is still possible to also derive a noun from the still valid other meanings (e.g. Das Abkommmen von der Fahrbahn führte zur Kollision) but we do not use this too often, probably to avoid confusion.
Another interesting side note on this is that another noun derivation from the verb abkommen was Abkunft which today is almost exclusively used in the meaning of descent but was at times also used as a synonym for Abkommen.
That is very much interesting, because it's not clear at all, and even I stumbled when I saw your question.
According to the German Wiktionary, the original meaning of the noun was von einer (finanziellen) Schuld abkommen/lösen, i.e. to pay back one's debt. This usage makes it clear, what you're deviating from.
A century later, the meaning of the noun had shifted from a deal to clear debts to a deal in general and further formalised to mean treaty of any kind.
