one of the oldest written words in the english language still in usage

[Michael Adams]

All right, keen-eyed Josh, you have me at a disadvantage, since I haven't a copy of the OED at hand.  But isn't your 601 evidence for "town" from "Aethelbert's Laws"?  If so, haven't you overlooked the closed lexical categories?  Surely you'll find the whole range of English prepositions, one or more conjunctions ("and," "[yogh]if"), the "definite article" or demonstrative adjective "[thorn]e," and other such words in the same text.  All of the earlier texts are interlinear glosses, I think, so constitute a different sort of evidence, but let's say, for the sake of argument, that they are indeed the first written "uses" of the words in question -- does none of the glosses include a preposition?  It would be odd if none did.  I would look at OED entries for prepositions and conjunctions before asserting that some noun or other is the oldest written word.

Nouns are so full of themselves; sorry, but I just feel that it's my responsibility to stand up for the little words.