Modern derivation of the Old English word 'frod', pronounced with a long 'o,' reintroduced into popular usage by Douglas Adams. It isn't possible to know whether Douglas Adams actually knew of the Old English predecessor to his coinage, but the word had almost the same meaning in Old English: wise, experienced--in general, a really together with it kind of guy!
There's a frood who really knows where his towel is. Or, þær biþ anum frodige mon hwa ful cynneþ hwær biþ byrnie him.
Hence a phrase which has passed into hitch hiking slang, as in "Hey, you sass that hoopy Ford Prefect? There's a frood who really knows where his towel is."