Just remembered that I owe y'all this post...

So Old English has strong verbs and weak verbs.  Weak verbs are derivatives, some from nouns and some from other verbs.  They were originally formed by adding a suffix indicating agency to whatever the original word was, but the suffix eventually became assimilated into the rest of the word, either mutating the vowel or geminating the consonant.  So, for example, to get the verb that became "deem" in Modern English from the word for "doom," "judgment," or "choice":

dōm + -jan à dœman à dēman

(The œ should be long, but Palatino doesn't have that symbol. :P)  "Deem," then, literally means "to make doom" or "to make a judgment."

When the process is applied to verbs, one uses the first (singular) past; it usually turns an intransitive strong verb into a transitive weak verb.  So, for example, to turn "sit" into "set" and "lie" into "lay":

sittan – sæt + -jan à settan

licgan – læġ + -jan à lecgan

So literally, "set" is "to make sit" and "lay" is "to make lie."
And there you have it. :)